2001 lincoln LS V8 Code # 1299

The car overheated once and now it continually runs about mid range on temp gage. I have no heat when it is turned up to 90 inside the car, it is running great but not sure where to start. I have checked coolant level and also pressure tested everything there is fine. I have ordered a cylinder head temp sensor and a heater core, as well as a new thermostat. pretty sure its not just a thermostat. What would you recommend

Welcome to the forum!

You might have a Dual Coolant Control Valve (DCCV) that is stuck closed, not flowing any coolant through the heater cores.

-Rod

Welcome to the forum!

You might have a Dual Coolant Control Valve (DCCV) that is stuck closed, not flowing any coolant through the heater cores.

-Rod

what would be the best way to check the dcc valve

That's a good question. On my wife's, I hooked my scan tool up to the car and checked the HVAC system for errors and monitored the datastream readings. All the temp sensors appeared to be reading accurately, and the signal to the DCCV was changing, but the temperature was not. I swapped in another control head to be sure, as well as checked the position readings of the different doors. Everything checked out nominal, but obviously there was still an issue. So, I replaced the DCCV since it was about the only thing I hadn't changed. I took the old one apart and was able to verify that one of the valves was stuck.

Scan tools to query the climate control system are not really easy to come by, and I'm not aware of an easy way to test the DCCV. The DCCV runs around $160 from Fast Parts Network, so it's not a cheap part to "shotgun." Fortunately for me, it fixed the issue.

-Rod

Rod-
Did your wifes car blow any hot air in the car or was that even an issue, if your wifes car was blowing hot air it would be safe to say that it is the heater core that is causing my problem?

My wife's car was blowing very hot air (115 degrees F at the vents) on any setting other than 60 degrees F. At 60 degrees F (automatic), the air was cold.

The DCCV works in both directions. Well, I'm not sure that makes sense. The valve modulates the flow of coolant through the heater cores. If one or both of the valves is stuck closed, you will have very minimal (if any) coolant flowing through the heater corresponding heater core. However, if it is stuck open, you will have continuous flow through the core. I'm not sure how the modulation works, if it is a PWM square wave, or if it is a variable voltage that controls the flow. I suspect PWM. If that's the case, it makes a lot of sense how my wife's DCCV was failing. The sticking valve would work for zero% duty cycle (spring to hold it closed, as well as for 100% duty cycle. However, for fast switching in between, the valves would stick in the open position. It was obvious that at least one of the valves was rubbing the solenoid assembly.

So, in your situation, I'd say it could still be a faulty DCCV (due to the over-temp coolant when the engine overheated) or a coincidental wiring issue.

-Rod

My 2001 Lincoln LS today started blowing hot air out of the passenger side vents instead of cool air. If I set the temp to 60 it blows cool. I've read some of the previous posts (like the one below) about the DCCV, my question is where is this valve and is it a DIY job. Sounds like it regulates coolant flow which may not be a DIY job.

- Tom



You might have a Dual Coolant Control Valve (DCCV) that is stuck closed, not flowing any coolant through the heater cores.

-Rod[/quote]

The DCCV is located behind the radiator and low on the passenger side (US) subframe. It isn't too bad of a job if you have the necessary tools. A set of hose pinch-off pliers are very helpful so you don't need to drain the entire cooling system. You'll also find it a lot easier to replace if you put the car on jackstands and can work from underneath as well as from above.

Based on a recent experience I had with my wife's 2002, you may also want to consider that you may have a bad passenger air discharge temperature sensor. The temp sensor is the same as the driver's side air discharge temp sensor and the evaporator discharge air temp sensor. You may want to try swapping the driver's side and passenger side sensors and see if that changes the behavior. On hers, there was no diagnostic code either from the self test or according to the scan tool. However, the datastream for the climate control system on my scan tool showed a bogus reading for the evap air discharge temp sensor. I swapped that sensor with the passenger discharge sensor and the system started working fine. Bought a new sensor from the dealer for $16.19 (full MSRP) and all is well now. The dealer said they've never stocked that part, so they must not fail too often.

-Rod

I think I would like to try and swap the temp sensor first. Where do I find these sensors?

I have the same problem on my 2002 Chrysler Town & Country. The passenger side blows warm air if the temp is not set below about 68. Does this have a similar sensor?

Thanks,

Tom

The passenger air discharge temp sensor is located in the center plenum. To get to it you need to remove the passenger footwell trim piece which is held in place with two plastic push rivets. Then remove the one 8mm (IIRC) bolt to drop the floor vent. With that removed, stick your head under the dash and look to the center plenum area behind the radio and HVAC controls. The temp sensor will be an off-white color rectangular piece (all that's visible) with a two wire connector plugged in to the top of it. With a small, long flat pocket screwdriver, unplug the wiring then pry the side nearest the radio/HVAC controls away from the plenum. It will pop out slightly, at which time you can reach in and wiggle the sensor out usings a side-to-side motion. Do not twist/rotate the sensor.

There will be two more sensors just like it on the driver's side mounted in the plenum. Access and remove them in a similar fashion.

I'm not sure what the Town and Country will use or how it controls the heater core flow. I believe it just has a single heater core though whereas the LS has a dual core heater core and controls coolant flow for the driver's side and passenger's side independently.

-Rod

You can bench test this valve with 12V and use WD40 to clean + exercise.

They seem to lockup during the summer months when not being used.

MCGIVER

2002 lincoln ls ac blows hot air. Ran diagnostic and was given this code:

19 47

Any suggestions would be great

You can bench test this valve with 12V and use WD40 to clean + exercise.

They seem to lockup during the summer months when not being used.

MCGIVER

I have seen you recommend wd40 in several posts now - wd40 is not recommend as it is not sensor safe - meaning it coats sensors and is not meant for the heat range found in egines, engine bays.

the V8 uses a seperate electric coolant pump to circulate into the cabin - so... make sure to check out the fuses and then also check that pump.

if you PM me your e-mail address I'll send you a cooling system diagram and you can start from there.

Hey Quik LS, I would love to get my hands on a cooling system diagram. Could you email one to me too?

I'm having a heating problem with my '04 LS V8. When the engine first warms up, I get some heat. But as the engine gets warmer and runs longer, the air coming out of the vents becomes progressively cooler. If I drive long enough, the vents will eventually blow nothing but cool air, even if I have the ATC set on 90 degrees. The fan speed continues to run faster and faster because the system knows that it is not keeping up with the temperature setting.

The engine temperature gauge shows normal readings - the engine warms up quickly when cold and then the temperature needle remains in the normal mid-position at all times. Therefore I don't think I have a thermostat problem. However, if I hit the accelerator and rev up the engine, I suddenly get heat out of my registers.

Based on the symptoms, I think I have a cooling system problem. I suspect that I either have air in the system or I have a coolant control valve problem. Or, based on your last post, maybe I have an electric coolant pump problem. I noticed that my coolant level is very low, so the first thing I'm going to try is adding more coolant.

I took car to my dealer for him to fix this problem, and he didn't have a clue. At first he insisted that everything was operating normally. When I demonstrated to him that it wasn't, he said it was likely a very complex problem that would require tearing apart the dashboard and would be very expensive. I think he's entirely on the wrong track because I think this is a cooling system problem - not an automatic climate control problem. I don't think he even considered the cooling system, so I am stuck with trying to diagnose the problem myself. Thus a diagram to help me understand how the system is supposed to work would be very helpful.

Welcome to the forum!

Have you tried running the DATC self-diagnostics? If not, the procedure is posted elsewhere on the forum. Try performing a search for keywords "DATC self".

-Rod

Thanks for the suggestion shorod, but I suspect that my problem is simply the result of air trapped in the heater core. I bought some coolant yesterday to top off the reservoir, and it took 3 quarts. In light of the fact that the entire system capacity is only 11.9 quarts, I have to suspect that my heat problems are related to this. Adding the coolant seems to have helped the heat problem a bit, but it has not entirely solved it. Since the system was so low on coolant, it seems like my first order of business should be bleed out any air that may have entered. I'm hopeful that this will solve my problem. If not, then I will have to move on to other possibilities. Now I need to do a little searching on this forum to figure out the best way to bleed any air out of the cooling system.

Ahhh, that would make sense. Good find.

3.9L engines




Remove the engine fill cap.

3.0L engines


Open the engine air bleed.

Open the heater air bleed.
Add coolant to the degas bottle allowing the system to equalize until no more coolant can be added.

3.0L engines


Close the engine air bleed when coolant begins to escape.

Install the degas bottle cap.
CAUTION: Care must be taken to make sure the accessory drive belt does not become contaminated with engine coolant.

Add as much coolant as possible to the engine fill. The heater air bleed will remain open.
Install the engine fill cap.
Install the engine fill cap until contact is made, then tighten an additional 45 degrees (1/8 turn).
NOTE: The heater air bleed remains open. Start the engine and turn the heater to the MAX position.
Close the heater air bleed when a steady stream of coolant escapes during engine idle.
Allow the engine to idle for five minutes, add coolant to the degas bottle as needed to maintain the cold fill MAX mark.

Open the heater air bleed to release any trapped air and close again.

3.9L engines
Maintain engine speed of 2,000 rpm for 3-5 minutes or until hot air comes from the heater.
Return to idle and verify hot air is still coming from the heater.

3.0L engines
Maintain engine speed of 1,500 rpm for 3-5 minutes or until hot air comes from the heater.
Return to idle and verify hot air is still coming from the heater.

All engines
Set the heater temperature setting to 24°C (75°F) and allow the vehicle to idle for two minutes.
Shut the engine off and allow to cool.
After the engine has cooled, add coolant to the degas bottle to bring the level to the cold fill MAX mark.

-Rod

The problem with erratic, insufficient, or no heat with my '04 LS V8 continues. I am stumped, so any suggestions would be appreciated.

Here are the symptoms. The automatic temperature control system works fine for about the first 20 minutes of driving after starting a cold engine. Then the air temperature coming from the vents gradually becomes cooler until they are blowing nothing but cold air. The blower motor ratchets up to full speed because the system knows that the cabin temperature is falling behind the set temperature. As I move the temperature setting up, the air discharge temperature moves up slightly . . . for a few minutes. Then it goes cold again. This procedure continues until I have the temperature setting up to 85 degrees. Eventually the air goes cold even with the ATC set at 85 degrees, even though the cabin temperature is only 55-60 degrees.

If I push the ATC temperature setting from 85 to its maximum setting of 90 degrees, there is suddenly abundant heat, and the heat continues for as long as the temperature is set a 90. As soon as I reduce the temperature setting to 85, the air from the vents goes cold again, even though the cabin temperature is only 60 degrees. The blower motor continues to run at full speed throughout this whole exercise as the system tries desperately to bring the cabin temperature up to the set temperature.

I thought that I had discovered the solution to this problem a few days ago when I noticed that my coolant was very low. I figured that the low coolant level had probably allowed air into the system causing a vapor lock in the heater cores. After adding 3 quarts of coolant and bleeding the system through the heater hose bleed valve next to the coolant reervoir, I figured that my problems were fixed. But it soon became apparent that they weren't.

I have considered the possibility that I may still have air in the cooling system, and that I need to bleed it some more. However, in light of the fact that I can get abundant heat out of the system at any time when I push the temperature setting to 90 degrees, it seems unlikely that the problem could be an air lock in the heater core.

The engine temperature gauges behaves as it always has. After a cold start, the needle moves up to the midway position after a few minutes and stays there. Warm air from the heater comes very fast, as it always has, within a couple of minutes. The problem is that the warm air eventually turns cool. It seems to make no difference whether I'm driving or idling, and racing the engine at 3,000 rpm also seems to have no effect.

I don't know whether this has anything to do with the problem, but I've noticed that the face of the ATC panel on the dash becomes increasingly warm to the touch as the engine runs longer. After a 2-hour drive, it is actually hot to the touch. Is this normal, or is it a sign that something might be wrong with the control panel? Shorad, you suggested in a previous post that I try running the DATC self-diagnostics which I should be able to find by searching the forum. I tried searching but could not find what you were referring to.

Any suggestions would be appreciated. Winter is coming, and I don't want to be driving around here in Maine with no heat. Like I mentioned in a previous post, I took the car to my local Lincoln dealer to service the problem a while ago, and he was totally useless.

Rod, I don't if you've had a chance yet read my post above, but I finally found instructions on how to do a DATC self-diagnostic for a 2004 LS. The problem is that I don't know how to interpret the results. I took photos of the results, but I don't know how to attach photos to this post, so I'm giving you a link to an online 2-photo slideshow showing the results. Sorry, but it's the only way I could figure out to show you the info. Let me know if the results offer any clue about my heating problem. file:///C:/DOCUME%7E1/Rick/LOCALS%7E1/Temp/moz-screenshot.jpgfile:///C:/DOCUME%7E1/Rick/LOCALS%7E1/Temp/moz-screenshot-1.jpghttp://www.photoshow.com/watch/qs5Te4Sx

Rod, upon doing further research, I see that results in my photos simply indicate that everything is working properly. I understand that the self-test procedure does a hard reset of the system, so perhaps that will help. I'm running out of possible reasons for my heat problems, so let me know if you have any ideas.

It appears you have a problem with the photo links. It looks like the links to the images are still on your harddrive and I don't find anything at the roxio photoshow link.

What your climate control is doing is almost the exact opposite of what my wife's was doing. On hers, we'd get heat on any setting until we set the controls to 60 degrees, at which time we'd get full cold. Since you get heat with the set point at 90, it sounds like the DCCV is working when it's commanded to open/close, it's just being commanded to close most of the time.

On my wife's, the problem was a bad evaporator air discharge temperature sensor. The sensor was always reading 255 degrees. Maybe yours is reading 0 (or whatever the minimum is). For what it's worth, hers did not have a diagnostic code, but I was able to monitor the sensors and door positions in the datastream mode of my scan tool. I would hope the dealer would have had the capability to do this too.... There are 4 sensors which are all the same part number. I swapped the evap air discharge sensor with the passenger air discharge temp sensor and the functionality of the system seemed to working working fine, so I bought a new sensor (around $22 from the dealer) and all's been well through the remainder of summer and into fall here in Iowa (fairly significant temperature swings). When I bought the sensor, the dealer had to order it and they told me that they've never stocked that part so it must not fail often.

-Rod

Rod, I'm not sure what the problem is with the photos. They're not on my hard drive, and the link in this forum works fine for me when I click on it. At any rate, the photos are irrelevant now that I understand that they're simply showing everything as normal.

I had considered the possibility of a bad sensor, but I would think that a bad sensor would cause this problem consistently. The problem that I'm having is erratic - not consistent. Like I said, everything works normally for about the first 20 minutes after I start my car. The only way that a bad sensor could be causing this problem would be if the sensor kept alternating from good to bad. I suppose that's possible, but it seems unlikely. I assume that the problem with your wife's car was consistent in that the vents always spewed heat unless you set the temperature at 60 degrees. With my car, I sometimes can't get heat unless I set the temperature at 90, but other times I can get heat when the temperature is set in the 70's.

By process of elimination, I'm suspecting that I may still have air in my cooling system. That's the only way I can explain its behavior. Perhaps it takes 20 minutes or so for the air to find its way into the heater core - I don't know. What puzzles me about that theory though is that, if air in my heater core is preventing me from getting heat, why do I suddenly get plenty of heat when I move the temperature setting to 90? I'm wondering if perhaps the 90 degree setting is that only one where the DCCV's actually open fully, and the fully open DCCV's somehow allow the coolant to pass through the air lock.

I don't know the answer, but tomorrow I'm going to try a giving the cooling system a really thorough bleed. I bought a plastic hose at the hardware store today. I'm going to open the heater bleed valve and connect one end of the hose to it, then I'm going to stick the other end of the hose into the coolant reservoir. Then I'm going to let the engine run for a half-hour or so with the DATC set at 90. Unless there's something about the LS cooling system that I don't understand, I would think that should remove any air. If that doesn't solve my problem, then I don't know what my next move will be.

I agree with your comment that the Lincoln service people should be able to figure out what's going on and where the problem lies by simply using diagnostic tools. But like I said, they first told me that everything was operating normally, and then after I demonstrated to the mechanic that it wasn't, he seemed puzzled and said that the only thing he could do was to tear my dash apart to see what he could find. His underlying message was, "do you really want to spend that much money on something that doesn't seem to me to be a big deal? I suggest that you learn to live with it."

If I can't figure out this problem myself, then I'll probably either take it back to the dealer and request a different mechanic, or I'll simply find another dealer to take it to. I'll let you know how I make out.

Rod, one more doubt about the bad sensor theory. If I had a bad sensor, wouldn't the automatic blower speed slow down (thinking that the temperature had been satisfied)? My doesn't. It continues on high speed trying to bring the cabin up to the proper temperature.

When your wife had the problem with her car, how did her blower speed behave when set on automatic?

Sorry for the multiple posts, but my mind keeps working after I make a post, and I think of new arguments to add.

I understand that the LS has separate sensors to maintain separate driver and passenger temperatures. If a sensor went bad on one side, I would think that the other side would still operate properly. With my car however, both the driver side vents and the passenger side vents behave exactly the same. I suppose that I could have intermittently bad sensors on both sides, but that seems like a stretch.

I don't remember how the blower operated with my wife's set to automatic. I seem to rememeber hers blowing full as well because there was such a drastic difference between the set points for driver and passenger sides and the evaporator discharge temp. The evaporator air discharge temp sensor is not different for driver and passenger side. That is the sensor that was reading 255 degrees. I then swapped that sensor with the passenger air discharge temp sensor and the system seemed to function correctly (so it worked once the bad sensor was moved to the passenger air discharge temp position).

If the evap air discharge temp sensor on your car was reading low temp, that might explain why you have exactly the opposite operation as my wifes. The intermittancy could easily be due to a loose connection or a solder joint within the sensor that opens up after a few minutes.

One way to look at it is the cost of the sensor be less than half an hour of the dealer's diagnostic time and will only take about 15 minutes to change out. Plus, if that doesn't fix it, you now how a spare sensor that you can move to the 3 other locations to see if that has an effect.

I don't usually recommend shotgunning parts, but if you don't have access to a profession scan tool at no cost to you, the cost of this shotgunning way outweighs the cost to have a scan tool connected to the system.

You could also check the voltage to the DCCV if you have a fast DMM or better yet, an oscilloscope. If you verify that the DCCV is not being commanded to open at any setting other than 90 degrees, then you know the issue is not solely an air pocket.

-Rod

Those sound like great suggestions Rod, and I will definitely give them a try. In regards to checking the voltage signal to the DCCV, why does the DMM have to be "fast"? If I am unable to detect any change in voltage when I change the temperature setting, is that necessarily an indication that the there's a problem with the DATC system, is it possible that the DCCV is controlled by something other than changes in voltage?

I like the idea of swapping the temperature sensors around. That could be the culprit.

Do you agree that the DCCV is likely fine in light of the fact that I can always get heat from the system if I push the temperature setting high enough?

Yeah, I don't think the DCCV is your culprit since it reliably works at the high set point. The DCCV is modulated by voltage from the DATC control unit. When each valve of the DCCV receives battery voltage, it shuts off the flow of coolant. The amount of flow is modulated, so to get a good feel for if the DATC module is commanding the DCCV, you'd want to be able to see the pulse width changes with the DMM. To read something other than "mostly battery voltage" or "no voltage" the meter would need to be pretty fast.

The Red/Orange wire for the DCCV is hot all the time. The Brown/Green wire is for one of the valves and the Brown/Blue wire is for the others. The DCCV switches the ground to modulate the valves. When you set the temperature to 90 degrees, you should read no voltage between either of the brown wires and the Red/Orange wire. That would indicate full coolant flow and that the valve is opening when commanded. However, this doesn't necessarily mean that it can switch fast enough to give the control a new, properly working valve would. That's where the oscilloscope would come in handy, to verify that the valve is not receiving a modulated voltage at lower temperature settings. That being said though, I'd still not recommend changing out the DCCV at this point yet.

-Rod

I bled my cooling system for a half-hour like I described, but the system is still doing the same thing. It works fine for the first 15 minutes after a cold start, then the outlet temperature from the vents starts getting progressively colder. The problem begins almost immediately when starting out with warm engine.

I don't know why I didn't think of this before but, when it started blowing cold air today, I opened the hood to check the temperature of the water pipes between the DCCV and the heater cores. They were all so hot that I couldn't touch them. That would seem to confirm theres plenty of hot coolant flowing through the heater cores, but the heat blender door must be closed. It can't be stuck because I get plenty of heat when I push the temperature setting to 90. I also listened carefully with the blower on low and the radio off as I alternately changed the temperature settings back and forth between 60 and 90. I was listening for some sounds of a sticking door, but I couldn't even hear it move. There was nothing but silence as the system alternated between blowing cold air and blowing hot air.

Therefore something must be sending a false signal to the bypass door to make it close up after the system runs for a while. Your suspicions about a bad sensor would seem to make sense (pardon the pun), but I'm not sure how to get at them. I read your post earlier in this thread with instructions about how to access them but, either I don't understand or my car is different. Since my LS is a bit newer than yours, I wonder if the hvac system may be built differently. I don't even see the footwell trim piece that you refer to. When I stick my head under under the dash on the passenger side, I can see the blower motor and where it connects to the air ducts, but that's about the only thing that I can positively identify. Everything else is a mystery.

Do you know exactly what controls the blender door? Is it one of those sensors and, if so, do you know which one? Any idea on how I might get instructions to access the sensors?

Lastly, I was thinking about how ridiculous this is that I'm forced into trying to fix this problem myself. Is there any good reason why this shouldn't be a simple fix for a mechanic who knows what he's doing and has access to all the diagnostic gear, wiring diagrams, and disassembly instructions? Wouldn't the proper diagnostic tools tell him exactly where the problem is without having to rip apart my dash searching for it?

Rod, I finally found two of the temperature sensors - the evaporator discharge temperature sensor on the driver's side, and the passenger heater core discharge temperature sensor on the passenger side. I know exactly what each one is because of the DTC's that are thrown out when I disconnect them. What was throwing me off in your previous instructions on how to access them was the removal of a knee panel. On my 2004 LS there are no knee panels in the footwells - it's all open when you stick your head underneath (a cost-saving change, no doubt).

I cannot find the driver heater core discharge temperature sensor. In a previous post, you said it was on the driver's side of the center air plenum near the evaporator discharge temperature sensor. Do you recall if it was upstream or downsteam of that sensor or how far away? I've poked my head around up inside there with a mirror, and I can only see the one sensor.

I'm thinking that the most logical culprit is the evaporator discharge temperature sensor. The reason that I'm less suspicious of either of the 2 heater core discharge temperature sensors is because the drivers side and the passenger side temperatures both behave exactly the same. Both sides blow cold air after the car has run for awhile. Seems like that would require both heater core sensors to go bad at the same time, and that seems unlikely.

The evaporator discharge temperature sensor is also the easiest to access. Nevertheless, since you indicated in a previous post that these sensors are quite inexpensive, I'm thinking that perhaps I should simply replace all 3 instead of poking around up inside there swapping things around. It's not a fun place to work. Do you have a part number?

If anyone knows how I can get my hands on an automatic climate control wiring diagram, that would really help to expedite my troubleshooting and pinpoint the problem. Half the problem I'm having in finding a solution is that I don't really understand exactly how the system is supposed to operate.

The car I was working on was my wife's 2002. There were 3 identical sensors on the driver's side and one on the passenger side. I no longer have my 2004, so I can't see if there were two or four sensors on it. That also has me wondering if the same part number is used for her 2002 as would be in your 2004.

If you send me a private message with your e-mail address, I should be able to provide you with the wiring diagram for the system.

-Rod

I took a look at the manual and there should be at least two sensor on the driver's side, the Evap discharge sensor and the driver's discharge temp sensor. Both are under the dash, mounted to the center plenum. They would appear to be within inches of each other. On the passenger's side there is one sensor, the passenger air discharge temp sensor. The driver and passenger sensors are probably mounted after the evap sensor in the air flow to sense the air temp coming from the vents. Unfortunately I knew the sensor I replaced was bad so I didn't save the part or the box to avoid the possibility of using it at a later date not knowing if it was good or bad.

There's also a 4th sensor mounted near the ignition key cylinder switch which is the cabin temperature sensor.

-Rod

Rod, I finally found two of the temperature sensors - the evaporator discharge temperature sensor on the driver's side, and the passenger heater core discharge temperature sensor on the passenger side. I know exactly what each one is because of the DTC's that are thrown out when I disconnect them. What was throwing me off in your previous instructions on how to access them was the removal of a knee panel. On my 2004 LS there are no knee panels in the footwells - it's all open when you stick your head underneath (a cost-saving change, no doubt).

I cannot find the driver heater core discharge temperature sensor. In a previous post, you said it was on the driver's side of the center air plenum near the evaporator discharge temperature sensor. Do you recall if it was upstream or downsteam of that sensor or how far away? I've poked my head around up inside there with a mirror, and I can only see the one sensor.

By sticking my head under the dash on the drivers side, I can see pretty much that entire side of the center plenum. The only temperature sensor that is visible is the evaporator discharge temperature sensor. If there's a heater core temperature sensor in the vicinity, then it must either be on a different side of the plenum that I can't see, or it's buried someplace inside a device housing. There is an actuator right near the evaporator discharge temperature sensor, and there's a plastic housing next to the actuator. I assume that the housing is for some kind of door operating assembly (perhaps the blender door?), and perhaps there's also a heat temperature sensor inside there too. I just don't know how the system components are laid out.

The more I think about this, the more I am inclined to discount the likelihood of a temperature sensor problem anyhow. It seems inconsistent with my symptoms. The temperature sensor is simply a resister - either it works or it doesn't. If I had a bad temperature sensor, that would not explain why my system works perfectly for a while. If there were a bad connection to the temperature sensor, that would explain erratic behavior, but my problem is not really erratic. To the contrary, it's actually quite predictable. After the engine has run for 15 minutes or so, the outlet air temperature begins getting progressively cooler. If I move the temperature setting up, the air will warm a little for a few minutes before turning cooler again. That procedure continues until finally I've got the temperature setting pushed up to 85, and all the outlets are blowing 50 degree air. When I push the temperature setting to 90, then I get all kinds of heat out of every outlet.

So I'm thinking that the symptoms suggest a problem with the heat blender door position. It seems that the heat blender door is positioned properly for the first 15 minutes or so that the engine runs, but then it gradually starts to close. I know that my heater cores are getting plenty of heat because the coolant pipes that connect them are very hot. And I know that the blender door isn't sticking or operative because they always open fine if I push the temperature setting up to 90.

So then I have to ask what is causing the heat blender door to mysteriously close up after a while? Again, I don't really understand what controls the door, but I assume it's an actuater that receives a signal from the ATC module. Therefore, I'm suspecting that my ATC module may be bad. The fact that the display of the ATC module has always become quite hot after a long trip also makes me suspicious. No one on this forum has indicated whether or not that is normal.

Normally, the only purpose of the evaporator discharge temperature sensor in any air conditioning system is to shut off the compressor before the evaporator coil becomes so cold that it ices up. So I doubt that's my problem here. I also doubt that I have a heater core temperature sensor problem because both the driver and passenger sides behave identically. That would mean that both heater core temperature sensors would always have to become faulty at the same time to produce the symptoms that I'm getting, and that seems unlikely.

I am assuming that there is only one heat blender door. If you tell me that there are two separate heat blender doors for the driver and passenger sides, then that complicates things. I wish I could figure out some way to determine the position of the heat blender door when I'm having this problem before I go buy another ATC module, but I can't. Perhaps a bad actuator could cause the blender door to behave this way too, although I'm not really sure how. I'm not quite sure where I'll go from here.

I think you're beginning to understand why the dealership didn't offer much help. Just think if you were paying them for all their time diagnosing this. Of course their scan tool would allow them to monitor the various actuator positions and temp sensor readings, which is how I was able to zero in on the evap temp sensor on my wife's car.

I think at this point you're left with either shotgunning parts, or finding a scan tool that can access the HVAC components in data stream mode and seeing what happens when working versus not working.

-Rod

I think the answer is the scan tool and, assuming that the dealer has one, I think I'll take the car back to the dealer. I know a lot more about this problem now than I did when I first took the car in for this problem before. If you were able to use a scan tool to zero in on a faulty evap temp sensor on your wife's car, I don't understand why the dealer can't diagnose exactly what the problem is with mine. Their mechanic's comment to me about having to tear the dashboard apart to figure out the problem makes no sense. Perhaps I'll simply ask the dealer to assign another mechanic to it - or take it to another dealer. Is there such a thing as a special mechanic certification for climate control systems? If so,then I'll ask for someone who has it.

I'm not aware of any special certification for this type of diagnosis. With the scan tool, they may need to be able to record the various datastream parameters when everythings working properly, then again when it's acting up, and compare the two. That might be the hard part, getting them to drive it long enough to get it to act up. Be sure they clearly understand the symptoms so they know when it's working find versus when it is experiencing the issues.

-Rod

That shouldn't be difficult. In fact, they don't even need to drive it. All they need to do is start it up when its cold and then take some readings when the engine first warms up. Then simply let it run in the parking lot for a half-hour and take some more readings. They will then have readings when the system is working fine vs. when its blowing cold air. This is not a situation where the problem is difficult to duplicate.

So, in case I just get blank stares when I suggest that they take some "readings", can you tell me exactly what that means? What are "datastream parameters" and how does the scan work? Is this a procedure that any dealer mechanic should be capable of doing?

I'm not a mechanic, and I was capable of doing it with my aftermarket scan tool. ;)

I'm not fully familiar with the WDS or NGS tester that the dealership would use, but suspect it's conceptually similar to my OTC Genisys scan tool. With my tool, I connect it to the regular OBD-II diagnostic port under the driver's side dash. I then enter the appropriate information for the car and enter the "Climate Control" system. Once in that section, I have the option of checking diagnostic codes, gathering system information, going into the RepairTrac database, entering the datastream, or entering a customer datastream.

I would select "Datastream." This will display A LOT of real time readings of the various sensors, including the various temperature sensors, engine speed, battery voltage, the various climate control door positions, the temperature set point, DCCV duty cycle, etc. I can choose to display any of the readings on a graph (to check for trends), as a number, or on an analog dial gauge. I can also record a series of these datapoints to playback later or download to the computer.

Since I would expect if my aftermarket scan tool has these capabilities, the factory scan system would have at least this much capability as well, and that any of the technicians at the dealership are trained in using it. If they were to record the various readings after the car's sat in the lot overnight, then again when the car is malfunctioning, there's a good chance something may jump out at them as being an area for concern.

-Rod

Very interesting. I wasn't aware that a scan tool would yield that kind of detailed information. It makes no sense to be taking things apart and replacing components on a hunch when you can get that kind of definitive information. I checked out the OTC website and watched their demonstration video on the Genesis. Pretty impressive.

I agree that one would think that the dealer's diagnostic equipment would be at least as sophisticated as your aftermarket scan tool. I'm going back to the dealer and insist that they diagnose this problem properly. I am able to give them a lot better description of the problem than I could before, and the problem is easily demonstrated. I'll let you know how I make out.

Good luck!

While you're insisting they properly diagnose the issue, you may want to get an estimate from them for the diagnosis. If you leave it open ended and they for some reason spend a bunch of hours looking into the issue, it could get expensive. It wouldn't surprise me if they charge you nearly $100 just to connect the scan tool.

-Rod

Brief update. I sent a very polite and friendly email mesage to the service manager at the dealership requesting his assistance. I explained everything about what was happening and requested that he contact me via phone or email. It's been 28 hours since I sent the message, and so far no response. Not encouraging.

On a more encouraging note, I think I've further narrowed the source of the problem. I don't know why I didn't try this before, but I discovered today that if I manually turn off the AC with everything else is in automatic mode, the outlet vent temperature turns warm like it should be, and the system seems to operate and regulate normally. When I turn the AC back on, the air temperature coming from the vents starts to plunge again. This discovery is making me suspect that the problem may be what you suggested way back in one of your earlier posts: the evaporator discharge temperature sensor. And fortunately that's the easiest one to access. Since these sensors are relatively inexpensive, I think I may replace it to see what happens. I think it's probably a safe bet that my dealer doesn't have it in stock, so I might as well just order it online someplace. Let me know if you have any suggestions on where to order it from.

I originally thought that the only purpose of the evaporator discharge temperature sensor was to keep the evaporator coil from getting so cold that it freezes it. That assumption was based on how household AC systems work, but perhaps automotive AC systems are different. Certainly if the sensor is sending a false signal to the EATC module telling it that the evaporator discharge temperature is very warm when its not, that could explain why the AC is coming on to cool the air. It would also explain why both the drivers side and the passenger side vents behave the exact same way. What is doesn't explain is why it takes 15 minutes or so after a cold engine start for this problem to begin. Perhaps that's how long it takes for the underdash temperature to warm up from the engine heat, and maybe that warmth is throwing off the temperature sensor - I don't know.

I've been pleased with the service from this online store (http://www.trademotion.com/partlocator/index.cfm?siteid=318). You can look up by application or by part number if you have the old sensor out.

-Rod

After further investigation, I don't think there's anything wrong with my evaporator discharge temperature sensor. I removed the device from my center plenum and put an ohmmeter on it. It seems to behave normally. I get a reading of about 50 ohms at room temperature. As I move the sensor to cooler or warmer locations, the resistance goes up or down in a linear fashion accordingly. Also, with the evap sensor missing from my climate control system, it still behaves exactly the same way - everything is fine for about the first 15 minutes, then the air coming from the vents starts getting progressively cooler.

I'm at my wits end trying to figure out what the problem is. I don't believe that there's a problem with either of my heater core temperature sensors because the drivers and passengers side both behave identically. I don't believe that there's anything wrong with the cabin temperature sensor because the blower speed increases as the difference between the cabin temperature and the temperature setting increases, thus confirming that the cabin temperature sensor is sensing properly.

About the only thing left that I can think of to explain what my system is doing is a bad EATC module. That has to be an expensive item, but at least the removal and replacement is easy.

Still no response to my email message to the dealer. Perhaps I need to find a different dealer. Someone with proper diagnostic equipment must be able to find the problem here so that I don't have to shotgun replacement parts. I wish I could find some literature explaining exactly how this system operates so that I could diagnose it more accurately based simply on what it is and isn't doing.

Since you've removed the Evap sensor, what's the harm in swapping it with one of the others? You may have read my other post where I didn't see a huge difference in ohmmeter measurements between the suspect sensor and the passenger sensor, but I swapped them and the system seemed to function properly. It would take you probably less than 15 minutes and would answer a question or two.

-Rod

Fair enough - I'll give it a try. I guess I must have forgotten about your previous post. I figured that a bad sensor would probably show either an open circuit or a short circuit or a steady resistance in all temperatures. I didn't realize that a bad sensor could still show a seemingly normal and varying resistance. I'll try swapping them.

The other thing that occurred to me is that maybe I'm making this all too complicated. If it appears that I cannot solve this mystery, perhaps I should simply resign myself to manually shutting off the AC and forget about it. The system seems to work fine in the current exterior temperatures (40-60 degrees) when I manually shut off the AC. Once the outside temperature gets below freezing, I don't think that the AC can run anyhow. It might become a problem when we get back into the air-conditioning season, but maybe not. It could also be a problem in damp weather trying to modulate the AC on and off to balance between dehumidification and a comfortable temperature. But I may opt for that inconvenience before spending hundreds or maybe over a thousand dollars trying to find a fix. Hopefully an easy solution will come soon.

Rod, as you suggested, I removed the passenger side heater core temperature sensor to swap with the evaporator discharge temperature sensor that I removed a couple days ago. Before making the swap, I put the ohmmeter on this sensor just like I did the other one. It seemed to behave normally, and I got the same exact resistance readings from both sensors. That convinced me that both sensors must be fine. Nevertheless I made the swap.

Dang, I couldn't believe what happened next. The heat worked fine for the first 15-20 minutes like it's been doing all along. Then I noticed that the air coming from the vents on just the passenger side started turning cool. As time went on, the passenger side air became progressively cooler, while the driver's side stayed at the same warm even temperature that it was supposed to be. That obviously confirms that my evaporator discharge temperature sensor was bad - just as you suspected! When I swapped that bad sensor into the passenger heater core discharge position, then I started having the identical problem with the passenger side only.

I don't understand it, and it makes no sense - but obviously I've got one temperature sensor that it not doing something that it's supposed to be doing. And I still don't understand the reason for the consistent 15-20 delay in the malfunction. But you nailed it. You da man!

I just ordered a new temperature sensor online for $9.93 plus $6.86 shipping. The parts place that you suggested in a previous post didn't seem to have temperature sensors, but this other place that I found does http://www.rockauto.com/catalog/raframecatalog.php . Thanks for all your help, Rod. I never did get any response to the message that I sent to the service manager at the dealership, so thank God I don't him anymore.

Glad to hear you're making progress, and hopefully this will take care of all the issues!

-Rod

My new temperature sensor arrived yesterday afternoon, and I installed it this morning. My climate control system now works flawlessly. Thanks again Rod for all your help. Without it, I likely would have spent many hundreds of dollars for diagnoses, tearing apart the dashboard, and replacing parts that have nothing wrong with them. And my frustration level would probably have been off the charts. Instead, it cost me $16 for a sensor and 5 minutes to install it. Like I said before, you da' man!

Hello everyone,

First time logging in here. I have a 2002 Lincoln LS with a V8. No heat from the heater. I have back flushed the heater core, replaced the thermostat and flushed the cooling system. The two inlet hoses to the heater core gets hot at the core and the outlet hose stays cold. My question is can the DCCV stop flow from the heater core? One more thing, when I accelerate hard, hot air will blow from the vents and as soon as I slow down it's back to cold air.

Hello everyone,

First time logging in here. I have a 2002 Lincoln LS with a V8. No heat from the heater. I have back flushed the heater core, replaced the thermostat and flushed the cooling system. The two inlet hoses to the heater core gets hot at the core and the outlet hose stays cold. My question is can the DCCV stop flow from the heater core? One more thing, when I accelerate hard, hot air will blow from the vents and as soon as I slow down it's back to cold air.

Your last sentence makes me suspect you have air trapped in the cooling system, which could at least contribute to your issue.

-Rod

Your last sentence makes me suspect you have air trapped in the cooling system, which could at least contribute to your issue.

-Rod


Thanks for the tip. I tried to bleed the system but I don't know if I did it right. I opened the air bleed, filled both the degas bottle and engine fill and ran the car at idle till a stream (not constant) was coming out of the air bleed. When I'm in the gas, I get hot air. But, as soon as I let off the gas back to idle, the air starts to get colder. The good news is that the outlet hose at the heater core is hot. Is there a better way to bleed the system?
Thanks for your help.

The procedure from the factory service manual:

1. Remove the engine fill cap.
On 3.0L engines
2. Open the engine air bleed.
On all engines
3. Open the heater air bleed.
4. Add coolant to the degas bottle allowing the system to equalize until no more coolant can be added.
On 3.0L engines
5. Close the engine air bleed when coolant begins to escape.
On all engines
6. Replace the degas bottle cap.
On 3.9L engines
CAUTION: Care must be taken to ensure the accessory drive belt does not become
contaminated with engine coolant.
7. Add as much coolant as possible to the engine fill. The heater air bleed will remain open.
8. Replace the engine fill cap.
On all engines
9. NOTE: The heater air bleed remains open.
Start the engine and turn the heater to MAX position.
10. Close the heater air bleed when a steady stream of coolant comes from it, during engine idle.
11. Allow the engine to idle for five minutes, add coolant to the degas bottle as needed to maintain the
cold fill MAX mark.
12. Reopen the heater air bleed to release any entrapped air and close again.
On 3.9L engines
13. Maintain engine speed of 2,000 rpm for 3-5 minutes or until hot air comes from the heater.
14. Return to idle and verify hot air is still coming from the heater.
On 3.0L engines
15. Maintain engine speed of 1,500 rpm for 3-5 minutes or until hot air comes from the heater.
16. Return to idle and verify hot air is still coming from the heater.
On all engines
17. Set the heater temperature setting to 24°C (75°F ) and allow the vehicle to idle for two minutes.
18. Shut the engine off and allow to cool.
19. After the engine has cooled, add coolant to the degas bottle to bring the level to the cold fill MAX
mark.

-Rod

Rod or Hanson,

GREAT post! I have been having the same issue with my 02. Is there any info you guys can email me on what I need to do to get this fixed?

My new temperature sensor arrived yesterday afternoon, and I installed it this morning. My climate control system now works flawlessly. Thanks again Rod for all your help. Without it, I likely would have spent many hundreds of dollars for diagnoses, tearing apart the dashboard, and replacing parts that have nothing wrong with them. And my frustration level would probably have been off the charts. Instead, it cost me $16 for a sensor and 5 minutes to install it. Like I said before, you da' man!

Which issue are you having, the 1299 code or the just climate control heat/cool issues without any specific code? Have you read through the 4 pages of this thread and tried the various suggestions?

-Rod

Just the climate control issues. My A/C blows COLD unless I set it ti 90, then it blows HOT. And it doesn't help that I am ignorant about cars.....



Which issue are you having, the 1299 code or the just climate control heat/cool issues without any specific code? Have you read through the 4 pages of this thread and tried the various suggestions?

-Rod

If you send me a private message with an e-mail address that can accept PDF files, I can send you the little cheat sheet I put together when I was troubleshooting my wife's temp issues.

-Rod

If you send me a private message with an e-mail address that can accept PDF files, I can send you the little cheat sheet I put together when I was troubleshooting my wife's temp issues.

-Rod

Per your PM, the file should be in your inbox.

-Rod

The procedure from the factory service manual:

1. Remove the engine fill cap.
On 3.0L engines
2. Open the engine air bleed.
On all engines
3. Open the heater air bleed.
4. Add coolant to the degas bottle allowing the system to equalize until no more coolant can be added.
On 3.0L engines
5. Close the engine air bleed when coolant begins to escape.
On all engines
6. Replace the degas bottle cap.
On 3.9L engines
CAUTION: Care must be taken to ensure the accessory drive belt does not become
contaminated with engine coolant.
7. Add as much coolant as possible to the engine fill. The heater air bleed will remain open.
8. Replace the engine fill cap.
On all engines
9. NOTE: The heater air bleed remains open.
Start the engine and turn the heater to MAX position.
10. Close the heater air bleed when a steady stream of coolant comes from it, during engine idle.
11. Allow the engine to idle for five minutes, add coolant to the degas bottle as needed to maintain the
cold fill MAX mark.
12. Reopen the heater air bleed to release any entrapped air and close again.
On 3.9L engines
13. Maintain engine speed of 2,000 rpm for 3-5 minutes or until hot air comes from the heater.
14. Return to idle and verify hot air is still coming from the heater.
On 3.0L engines
15. Maintain engine speed of 1,500 rpm for 3-5 minutes or until hot air comes from the heater.
16. Return to idle and verify hot air is still coming from the heater.
On all engines
17. Set the heater temperature setting to 24°C (75°F ) and allow the vehicle to idle for two minutes.
18. Shut the engine off and allow to cool.
19. After the engine has cooled, add coolant to the degas bottle to bring the level to the cold fill MAX
mark.

-Rod

Thanks for steps Rod,

I performed the steps twice and had the same results. I never got a steady stream of coolant on Step 10. Whenever I maintained the engine speed at 1500 RPM, the air was hot. Whenever I returned the engine speed to idle, the air blowed luke warm. What do you think? Still have trapped air in the system?
Thanks,
Cliffkat

can you pleeeeeease send me the same cheat sheets i have no owners manual and i want to bleed the coolant system and need to know what parts are which?