'98 rear air - not dash switch

Hey guys,

This is a re-post of sorts. I renamed it to make it stand out from the typical dash switch issue.

I was having the typical Windstar rear A/C issue.....hot air only out the bottom. I replaced the switch on the dash and I am now able to control where the air comes out but it is still hot. What should I be looking at to fix that problem?




I checked the 4 lines that run under the belly of the van and into the control area in the middle row driver's side. None of them are cold. Shouldn't at least one of them be cold? The front air is blowing out at 43F. The low side pressure is only about 40 psi with outside air temperature at 90F. It should probably be closer to 50psi for optimum cooling.

Is it possible the low pressure is the problem with the rear air, or is it more likely that I have a clog somewhere in the lines?

Is anything else going on behind that panel besides flipping the blend door? I know that is working since I can control where the air comes out and I removed the panel and witnessed the door’s operation.

Thanks in advance for any help.

Chris

Update: I added two lbs of freon to the system. That dopped the air temperature at the front about 4F and got the pressure to within specs (about 40 psi at 80F outside air) but had no impact on the rear air's ability to do anything. I checked on another Windstar and sure enough, one of the 4 lines that runs under the belly is cold when the rear air is functioning. So now I don't know what else to try.

Any ideas?

Thanks

Since the Windstar has two evaporators in it, I would think it could have two eveporator core orifices. They have two filters in them, so it could be possible that it is plugged and the other one for the front is not. This is the only explaination I can think of at this time. If you are sure you have air going across the evaporator, but it is not cold but the front is, something is blocking the refrigerant flow. Sorry it doesn't sound too good.

Are you saying that even with being able to switch the air direction, you are getting the SAME temperature air out of the TOP as the bottom? The top won't cool down over time? That doesn't sound right. Hopefully, somebody has or could send you a vacuum and electrical diagram of the back system and a schematic of the air handler with its contols etc. On some years, they put a valve underneath to turn off the coolant to the heater, though I don't know how that helps. Maybe your system has something like that for the rear ac. I'm fairly certain my 95 doesn't.

The air out the bottom is actually heated air because it blows over the heater core in back. The air out the top is basically outside air temperature. The air is ducted correctly over the evaporator but the evaporator doesn't cool down. I am hoping there is some sort of stuck valve back there preventing refrigrant flow and not some kind of clog in the line. I didn't see a valve but that doesn't mean anything.

Thanks

I'm going to attach a link that might be helpful at Autozone.com. It shows a green vac line going to the rear air handler of the early model and a white line for the late model, to change the air direction from feet to wall and ceiling. That does work, directing air where it should? I have a 95 and I've never really heard it move back there, but I'm the one always turning the dial only hearing things up front. Mine too, only has a fan speed control and a little vent in the same assembly.

I don't see anything that would stop refrigerant flow that is supposed to. The pressure you gave seems reasonable. If the front is working, DON'T put any more refrigerant in it! I am seriously concerned you have overcharged your system. Was the front ac cold as it should be originally? If yes, I really think you have overcharge it. Just because you have "good" pressure at the low side service port, doesn't mean you don't have the high side too high as the ac system is designed to ONLY come on at 45 psi or higher and will ONLY shutoff when it goes DOWN to 25 psi under ANY circumstances, at the low side. So, when it is cycling, the low side pressure will ONLY cycle betwen 25 psi and 45 psi. Anything else may be cause for concern that the cycling switch is bad, poor cooling will occur and possibly damage to the system. HOWEVER, the high presure side, which is right at the discharge side of the compressor, does have a safety switch that will shut down the compressor if the pressure gets too high, like with an overcharged or plugged system. In addition, there is an emergency pressure relief valve attached to the compressor when the pressure exceeds that of the safety cutoff switch.

Baring something else that I don't know about, I'm really thinking your evaporator core orifice is plugged. I don't know where it is for a fact, but based on what I do know, i'd expect it to be in the wall with the evaporator. I would suggest you check your lines more closely underneath and see if there is any temperature difference between the two lines to see if any refrigerant is moving after running the van for awhile. The smaller line is the one approaching, and will be hotter, and the larger line will be the one leaving the evaporator and will be colder if there is any flow.

Opps, I almost forgot!?! :shakehead
http://www.autozone.com/addVehicleId,2176302/initialAction,repairGuide/shopping/repairGuide.htm?pageId=0900c152800ae23b

Good luck. You may need prayer on this one! :D
Keep us posted.

Triplet, thanks for the information and the link,

The vacuum to the rear air handler is working correctly and will allow me to send the air to the floor or to the sides/ceiling.

I hope you're wrong about over charging the system. What you said makes sense though since the system will only run within a certain pressure range. The front air was running in the mid 40 degrees. It dropped down to about 41F when I added the extra freon. That's pretty chilly.

If I feel the lines going to rear air one of them is noticeably cooler than the other. Perhaps I should say that one is noticeably warmer then the other. Meaning that I don't think the "cool" one is cooler than outside air, but it's definitely cooler than the other line.

I think you are right. I must have a clog in the orifice or something. I don't undertand how a closed system can run for 10 years and then all of the sudden get a clog in it. Must be magic.

Thanks again, if/when I figure it out, I'll let everyone know what it was.

These systems can tolerate/generate air temp as low as 35 deg F. Much lower, and things will be freezing up. Not good. Especially bad for the compressor. It's only made to compress gas. Liquids can't be compressed, only pumped. The refrigerant entering the evaporator orifice should be quite warm to hot. So that seems consistent with what you found. I can only speculate why the thing seems to have suddenly stopped working, other than it was gradual until it was noticeably not cool.

If you wish to keep after this, inside the side wall I expect the orifice to be located. I've added a descritipn of the original and replacement of a bad one. I would expect them to look universally alike as the one in the diagram. Unfortunately, the resource won't let me include the diagrams. Sorry. :sad:


A/C Evaporator Core Orifice Replacement Kit Installation
1. Discharge the A/C refrigerant system as outlined.

2. Remove the condenser to evaporator tube (19835) from the vehicle.

3. Locate the A/C evaporator core orifice (19D990) by the three indentations or a circular recess in the metal portion of thecondenser to evaporator tube.


A/C Evaporator Core Orifice Location


4. Note the angular position of the ends of the condenser to evaporator tube so that it can be reassembled in correct position.

5. Cut a 63.5 mm (2-1/2 inch) section from the condenser to evaporator tube at the A/C evaporator core orifice location. Do not cut closer than 25.4 mm (1 inch) from the start of a bend in tube.

I highly recommend using a plumber's tubing wheeled cutter.

A/C Evaporator Core Orifice Section Removal From Liquid Line


6. Remove contaminants from the two pieces of the condenser to evaporator tube.

7. Lubricate O-ring seals with clean refrigerant oil and assemble orifice tube kit (with orifice tube installed) to condenser to evaporator tube as shown in the following illustration. Make sure flow direction arrow is pointing toward the A/C evaporator core (19860) end of the condenser to evaporator tube, and taper of each compression ring is toward compression nut.

A/C Evaporator Core Orifice Kit Disassembled

ÚÄÄÄÄÄÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄÄÄÄÄÄÄ ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿
³ Item ³ Part Number ³ Description ³
ÃÄÄÄÄÄÄÄÄÄÄÄÄÅÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÅÄÄÄÄÄÄÄÄÄÄÄÄÄ ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ´
³ 1 ³ 19835 ³ Condenser to Evaporator Tube ³
ÃÄÄÄÄÄÄÄÄÄÄÄÄÅÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÅÄÄÄÄÄÄÄÄÄÄÄÄÄ ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ´
³ 2 ³ -- ³ A/C Evaporator Core Orifice Housing ³
³ ³ ³ (Part of 19D695) ³
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³ 3 ³ -- ³ Compression Nut (Part of 19D695) ³
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³ 4 ³ -- ³ Brass Compression Ring (Part of 19D695) ³
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³ 5 ³ 19D990 ³ A/C Evaporator Core Orifice ³
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8. NOTE: The inlet tube will be positioned against the A/C evaporator core orifice tube tabs when correctly assembled.

While holding hex of tube in a vise, tighten each compression nut to 88-95 N-m (65-70 lb-ft) with a crow-foot wrench.

A/C Evaporator Core Orifice Kit Installed


9. Assemble the condenser to evaporator tube to vehicle using new green O-ring seals lubricated with clean refrigerant oil. Use only specified green O-ring seals at spring lock coupling.

10. Leak test, evacuate and charge system following approved procedure.

11. Check system for proper operation.

Thanks for the info. I looked it up on alldatapro and they have the labor as 1.5 hours. That means it'll only take me about 15 hours. I'm still on the fence but I think I'll give it a shot. It sounds "fun." I'll let you know what happens. Thanks again.

The rear expansion coil has a "thermostatic expansion valve" mounted to it that controls the flow of refrigerant into the coil. This valve is a bit more complex than the orifice used up front as it has a thermal bulb that opens and closes it. The valve separates the high and low pressure sides of the system. If the valve fails to open, there would be stagnancy and I would suspect the temperature of the tubes interring and leaving the coil would approach the temperature of the car body.

Gotcha. So it sounds like I am pulling the evaporator and the attached expansion valve. Hopefully (?) the problem is with that valve. I might get into it next week and will keep you guys posted. I saw pics of it on alldata and was thinking that would be the next logical step. Thanks a bunch!

It was the rear expansion valve. I ended up having to get the evaporator too. It was like $300 from the dealer. Thanks everyone for your help.

Oh yeah, I had a P0304 and pulled the upper intake manifold and cleaned it and everything is golden. This site is awesome. Thanks again.

Congrats on two jobs well done! Thanks for the feedback.

Did you do the work on the ac system?