2000 SEL: AC clutch not engaging when hot

When ambient temp is low (< 75F) AC works fine. When ambient temp is warm to hot, AC works for 10 to 15 minutes then blows ambient air. It appears that AC clutch is not engaging. When this happens, I disconnected the clutch cycle switch and jumped the connector. When I did this I could hear the fan came on, but the clutch still would not engage.

Any help is greatly appreciated.

EDIT: I should add that I also did a self-diagnosis (the floor-off then auto thing). The error code is 051 -- solar sensor open. Is that it? If so, how to I replace the solar sensor -- is it the same as the sunload sensor? Where can I find it?

Thanks.

Welcome to the forum!

From your diagnosis, it sounds like you probably have a bad clutch field coil that goes open when hot, but you'd certainly want to diagnose it further before replacing it. Did you jumper the low pressure switch or the high pressure switch? I don't think jumpering either of the pressure switches should have caused the radiator cooling fan to come on. Have you checked the low and high side pressures with a set of guages when the ambient temp is cooler and the sytem is working? Tripletdaddy recently provided an excellent write up in this Taurus forum of how the A/C system works, you may want to review that.

As for the solar radiation sensor, that would be the same thing as the sunload sensor. You can get one from the dealer or from the online stores such as this site (http://www.trademotion.com/partlocator/index.cfm?siteid=318).

-Rod

Thank you for the reply.

I only have a gauge that would attach to the low side service port so I checked pressure on the low side only. When the AC is working, the clutch cycles off at about 25 psi and cycles on at about 45 psi. I think that is normal from what I gathered from tripletdaddy's excellent writeup.

I also checked the low side pressure when it's very hot (>95 F) and the system not working, the pressure is 125 psi. Is this too high? Does that mean I overcharged the system? I did put in some R134 (less than a can) a few weeks ago, when I knew even less about AC. But to the best of my knowledge, the symptoms of the system have not changed, although I do believe the air is colder after the charge when it works.

I jumped the one on the top of the accumulator/drier I believe, in front of the the pressure tank. Are there two pressure switches? I thought there were two switches, one called clutch cycle switch on the accumulator/drier, another low pressure cutoff switch on the compressor?

Again, thank you for the reply. I have been reading the forums here and they are very informative.

Gees, you guys are making me blush with all of this attention!?! :redface:

Unfortunately, I don't have access to year specific info on yours to be precise with my accessment and diagnosis, so I will have to rely more on practice and earlier setups, but they should mostly be the same. I would need Rod to validate some of this, but first off, basically the sunload sensor helps the electronic temp controls figure out how to compensate the inside air temp for the sunload detected on the car. Ford says it is "located in the right hand upper outer finish panel" for a 95. After translation and verification on my 95, they mean in the top of the dash at the windshield. There are two identical locations for this thing in my dash, with my sensor on the LEFT, driver's side. I'd think even your year would be similar. If not there, then probably under or in the cowl vent area. Since the sunload sensor plays a role in the EATC cooling logic, it's conceivable it's your problem. As Rod said, your symptoms are strange and inconsistent with normal faults. Which for me, makes sense to have a bad electronics "smell" to it. Anything that seems to defy a reasonable explaination seems to lead to an electrical/electronic problem. Since you said the self test indicates the sunload sensor is open, you could verify that yourself with an ohms meter with it disconnected. If not open, there is a special resistance test that can be done, but it's something probably more familiar to Rod than me, due to it being a photodiode.

Like Rod said, I don't get you jumping the low side clutch cycling switch getting fan but no clutch. That doesn't jive with the sunload sensor problem. I'd have to see the wiring diagram on that. Possibly the PCM is being told by the EATC not to engage the clutch. You would have to completely bypass the clutch wiring with a hot and ground to verify if it works. Looking at a similiar year diagram, you possibly activated the low speed fan when you jumpered the clutch switch, because the PCM sensed the power supplied for the clutch. With that particular diagram, that is the only way the low fan could come on with the AC. The high side sensor/switch has four wires, usually by the compressor, and can turn on the high fans with a jumper to the correct pin holes. The other two are for shutting off the ac when too high pressure occurs, and will allow it on when the pressure is low enough.

The pressures you measured while it's running sound good. The 125 psi is posssible if it's hot outside. I'm more concerned why you felt you needed to add refrigerant originally. Was it not cooling very well? Try running your car in a very well shaded place to see how it works, possibly taking the sun sensor out of the equation. I'd like to know the temperature of the cold air, at max cool and fan speed. Look underhood for heavy sweating and frosting. Don't want lots of frosting!!! If you overcharged it, the high pressure cutoff would turn off the clutch, but should let it back on when it cools down and pressure equalizes. When it would stop working when hot, did it ever come back on, even after cooling off?

The thought of a bad coil is "chilling" as I had to change mine and was determined to do change in the car so I didn't have to discharge the system. Rod may be right, it is possible the coil "can't stand the heat" and a broken wire inside looses its connection when it gets hot.

Thank you for the reply. I was waiting for you to chime in and you did. :)

First off, I added refrigerant because it had the exact problem -- AC works for a while then blows ambient air when it's hot. Not even having the limited knowledge about AC I have now, I talked to a friend and he said due to the age of my car it was likely low on refrigerant. He told me adding R134 was a piece of cake so I did it.

Second, on the fan came on when I jumped the switch. Now that both you and Rod thought it's strange, I think I will need to double check. I really only heard a clicking noise when I jumped the switch and assumed it was the fan coming on. When I did the test it's already a little dark and definite without sunshine, I might have taken the sunload sensor out of the equation as you suggested.

Now I think about it, the noise might be the clutch trying to engage but failed to do so? Is that possible?

I think I will follow your advice and try to locate where the sunload sensor is in my particular model and do some test.

When it's truly hot, the AC would not come back on even after cooling off. The day I did the jumpering test, I came back from work at 5 PM and did the test after dinner -- a good 2 hours later -- and the clutch did not engage. That day was really hot and at 7PM the ambient temp was 95F. For a day this hot 2 hours may not be enough to cool off I guess.

No, I do not see much sweating and frosting under the hood. How/where do I measure the temp of the cold air?

Forgive me for not reading all the posting-- but when a/c quits after engine warms up- it is usually from a clutch armature plate air gap that is too wide- coil strength to pull in the clutch armature diminishes with heat- so an air gap of .060" will pull in cold- but after the first clutch cycle- and warm engine- the clutch will no longer pull in. The clutch wears is why the air gap widens- so next time it goes "warm" try bumping the front of the compressor with a wooden hammer handle or the like (while engine is running- but be extremely careful) or if access is limited, and you don't like trying to do this- then slam the hood- or do anything that would disturb the clutch- chances are pretty good the clutch will engage and this proves the air gap is too wide.

Clutch air gaps should be about .020" - depending on compressor- simply removing a shim behind the clutch can be the easiest solution

If in fact the fan came on, with you right over the engine, you should have heard a moderately high pitch humm, whir and feel and hear air moving as the fan pulled air into the engine compartment. Was the engine running when you tried this? It needs to be. The clutch makes kind of a metal to metal slapping sound. If all you heard was clicking, then you were simply energizing a relay(s). It would be a very good idea to locate the ac clutch relay and the two fan relays and verify they are good. It could be as simple as that. ie, the ac relay being heat sensitive/bad. But, I don't like coincidences, so the sun sensor is still not out yet for me.

You know the sweating and frosting would have to be after it working a little while, and gone rapidly in your kind of heat. Sorry, the center dash vent is where you measure the temp. Like I think I said before, if you take a ground wire and a hot wire to the clutch, with its wires removed, you should be able to jump start it enough to prove that it still works. In fact, do this with the engine OFF. All it will do is slap closed, but that's all you need to know. That would be a particularly good test if it stops working when it just had been.

Thanks for your input, brcidd (http://www.automotiveforums.com/vbulletin/member.php?u=356995). That hadn't occurred to me but makes perfect sense if it is just heat related. Do you know if an open sunload sensor can also cause this problem?

Sure, there are many variables- open sensors usually set HVAC codes- that flash control head displays- to indicate a problem-- is your control head doing anything amiss? I am more in tune to GM vehicles- but have wondered off into others at times....

I just play the percentages, the last dozen or so vehicles that I have fixed that have had your complaint (as you have described it) have almost all been wide air gaps-- you can replace the clutch, replace the compressor- and it will work-- but I always like to know exactly what is wrong and fix only what needs to be fixed- costs less money that way--and people seem to like that type of service.....

The system in discussion has an open sunload sensor fault code.

Thank you both for the replies. They are very informative. Boy, I will have a lot tests to do. :)

In addition to locating the relays and slamming the hood etc, I am thinking of getting a feeler gauge and getting down there actually measuring the air gap. How easy/difficult is it for an automotive newbie, but otherwise fairly handy person to do all this?

Thanks again.

-Leon

Update #1:

I checked the air gap, it's definitely too big -- 0.052 inches. Haven't done any other tests yet. I am going to try and fix it this weekend.

Thanks again for the help. Will keep you guys posted.

Just to be clear, you had previously said the ac is not engaging. Did you mean that you weren't getting cold air, or you did not hear it slapping on or did you see it try to turn on but wouldn't stay on when it got too hot? If it attempted to come on but couldn't pull together visibly, or a better test, you could measure the two wires are hot and grounded at the clutch but it wouldn't engage, then you very well may have a gap problem. Unfortunately, if it's down at the bottom, getting to it is a problem. The recommended procedure maybeis to recover the refrigerant so you can pull the compressor so you can remove the clutch plate to remove a spacer or two. But, there may be just enough room for jewelers hands and tools to remove the outer clutch plate to change the shims. On my 95, I really, really didn't want to remove the compressor to change the whole clutch. I did it. But it wasn't easy, and it was really tight. A real pita. If you are game, I don't think you could hurt too much attempting to do this bsides your knuckles and ambition. Ask around if someone you know has done this. Look on Autozone.com for reference in their repair section for your car, probably in the electrical section.

Thanks a lot for the information.

I did the switch jumping test again and hear a clicking/slapping sound, which I assume is from the clutch (coil?) and one I previously mistook as the fan came on. However the clutch still did not turn. So I think there is a good chance the gap is the problem.

Yeah, accessibility is a problem. I looked down there and it's hard to get to the wires. From above, there is less than an inch between the clutch and the wall. I have huge hands so I do not think I can get it done.

I also really, really do not want to remove the compressor -- don't have the tools to evacuate the system. So I am thinking of lowering the subframe and access it from below. Do you have any suggestions or tips?

Thanks,

-Leon

P.S.: I checked autozone and they don't have repair guide for 2000 Taurus.

Since it's been a long while, I can't remember if you should be able to turn the clutch end plate on the compressor or not. If you could watch what the clutch and compressor do when it engages, that might help. Does it slip, not turn at all, smell bad, sling stuff, etc.? That would be the case if the clutch is siezed, but the excessive gap indicates that it needs to be reduced. You may be able to remove the clutch plate as it is to then remove the necessary spacers. Or, you may be able to just unbolt the compressor so that you have enough room to work on the front of it. Chances are, the older Taurus at Autozone.com would be close enough to use as a guide for the repair.

Thanks for the suggestion. I lowered the subframe as far as I could -- about 2 inches -- but it's still not enough. Tomorrow I am going to unbolt the compressor and reposition it for better accessibilty.

I just came across the PM you sent me. Between AF database problems and my faulty web browsers, I haven't been getting any emails from them as before.

Looking at the posts, I think you should by now have gotten my last post that your PM indicated was missing. Where you able to do anything with the compressor? Just recently I worked on a friends Taurus that involved removing the clutch, coil and pulley. I was able to loosen the end bolt to the clutch plate with a 1/4" ratchet and 8mm or 5/16" socket. The clutch plate should slide right off no problem for setting the correct air gap with the tiny spacers (washers).

Thank you for the reply.

This appears to be a case that there might have existed multiple problems.

I was able to loosen the end bolt and re-set the air gap back to spec -- I set it to about 0.018.

The AC still wouldn't work when it's extremely hot! Well, it may be a little better but the general symptom stayed the same.

I then checked the pressure and it's low on froen again, so it appeared there was a leak. I took it to a shop and they found leaks around the service ports. Had the ports changed and the AC recharged. That particular day was cool -- the high was in the middle 60's -- so I couldn't tell if the problem was fixed but the AC definitely blew much cooler than before.

The next day it was hotter and to my disappointment the AC problem came back. So I took the car back to the shop and they did more tests but could not find any problem. So the technician unconnected and cleaned the connections, and reconnect them back.

To my surprise, this appears to solve the problem and the AC has worked since (knock on wood)!

So the technician unconnected and cleaned the connections, and reconnect them back.

To my surprise, this appears to solve the problem and the AC has worked since (knock on wood)!

Maybe the contacts got spread a bit when you jumpered the pressure switch?

-Rod

Maybe the contacts got spread a bit when you jumpered the pressure switch?

-Rod

The technician said he believed the problem was with the AC clutch relay. He said the relay wasn't bad, but it might have a loose/intermittent connection on one of its legs.

If that turns out to be the fix, it sounds like you found a good, honest shop/technician!

-Rod