A/C clutch staying engaged

[tweeder22n83]

Hey guys, first post on a great sight with lots of knowledge. I have an issue with my A/C on my 99 Explorer 5.0 XLT. I have had the coolant replaced in he last few days because it would not blow cold enough in this heat wave. I noticed that the air was cooler right away. While driving down the road the air was awsome. I pulled into the store on the way home and went inside. With the engine running and sitting still for about 5 minutes, the air was blowing hot. I continued home and it did good again. Once home I popped the hood and checked the clutch on the compressor. It was running and was not disengaging. I diconnected the high side switch and it quit running. I cleaned all of the connections and the problem continues. What would cause the clutch to not disengage?? Any input would be nice. Thanks guys

 

[my98nnj]

Your post is confusing.

You replaced the engine coolant or the R134 refrigerent?
When you idle the ac blows hot and when your moving it blows cold?
Is the compressor remaining engaged when you turn the system or engine off?

Please clarify.

 

[budwich]

IF you can cause it to disengage electrically (ie. by disconnecting a sensor) then its working the way it is suppose to. IF you turn off your AC (eg. choose the heater), is it still engaged??? IF it is you have a control switch issue.

 

[tweeder22n83]

Sorry guys, I've been gone a couple of days on business.

(1) What I meant to say is the refrigerant was changed in the A/C.

(2)It blows hot when sitting parked and will begin to blow cold when going down the road.

(3)The compressor stays engaged and does not click off while the vehicle is running.

(4)The compressor does shut off when the high side switch is disconnected. So the compressor is good I would think. Is there a low side switch that maybe is faulty?

Hope this helps and sorry for the confusing post.

 

[daizex]

I can't really comment on anything but the 3 point, my clutch is engaged the entire time I have the a/c running.

 

[tweeder22n83]

I just didnt know if the clutch was supposed to disengage. Maybe the brain children at the stealership didnt charge the system correctly. Thanks again guys.

 

[bobflood]

The clutch is supposed to cut off when low side pressure gets too low (this is the normal control to keep interior temp controlled and keep evaporator from freezing up), high side gets too high (safety) or at WOT (to eliminate power drain from compressor when engine power needed). I have opposite problem - compressor will not run at all - and my troubleshooting/sectionalizing has been nothing but frustrating as I can't seem to get repeatable, consistent results.

Low refrigerant usually results in the compressor "short cycling" rather than running all the time.

 

[derek_redneck91]

I took my AC compressor off. It never worked since I bought it so to hell with it! Another member on this site had taken a dyno test and showed up to a 20hp gain with it off. And there's more room in the engine bay!

 

[budwich]

The clutch is supposed to cut off when low side pressure gets too low (this is the normal control to keep interior temp controlled and keep evaporator from freezing up), high side gets too high (safety) or at WOT (to eliminate power drain from compressor when engine power needed). I have opposite problem - compressor will not run at all - and my troubleshooting/sectionalizing has been nothing but frustrating as I can't seem to get repeatable, consistent results.

Low refrigerant usually results in the compressor "short cycling" rather than running all the time.

Not to highjack someone thread... but Bob.... I am not sure I understand the two portion of the statement... "will not run at all" and can't get repeatable consistent results ??????? please provide more details and perhaps someone can help.

 

[bobflood]

Not to highjack someone thread... but Bob.... I am not sure I understand the two portion of the statement... "will not run at all" and can't get repeatable consistent results ??????? please provide more details and perhaps someone can help.

Compressor does not run in any AC mode. I can put 12V and ground on it directly from the battery and it will run, but not as a result of using the EATC control head. I looked at the wiring diagram and found several places along the compressor control circuit (AC Cycling Switch, AC Pressure Switch, WOT Relay, Compressor plug) where I could disconnect things and measure voltages. However, sometimes I would get a voltage reading, and then the next time not. The battery was wearing down and it was starting to rain, so some of that might have been "****pit" problems. I also did some continuity testing between pairs of these things and all appeared to be good. I probably need to write myself out a test plan and check things off/record results as I do them.

 

[RomeovilleIL]

Only way to really understand what is happening would be hook up a pressure guage. The situation you described sounds like a classic overcharge, but is also not uncommon with shadetrees that don't evacuate the a/c prior to filling and have an undercharge along with air in the system. The pressure will show high and keep the clutch engaged, but the pump cannot get the refrigerant to liquify so no cooling. Once the RMPs raise a little the pump runs fast enough to catch up and you get cold air again. Do you hear any hissing noise in the cabin when it blows hot?

 

[budwich]

OK... that's helps the "clarity" maybe... and "I see says the blind man". It would appear that perhaps you are not getting "stable" voltage out of your controller.... which is quite possible. Have you "dropped" it and taken a look inside to see any obvious "burns / cracks / etc" that might be a clue? Sounds like you might be in the "broken controller camps" of all those you have helped in the past ...

 

[bobflood]

OK... that's helps the "clarity" maybe... and "I see says the blind man". It would appear that perhaps you are not getting "stable" voltage out of your controller.... which is quite possible. Have you "dropped" it and taken a look inside to see any obvious "burns / cracks / etc" that might be a clue? Sounds like you might be in the "broken controller camps" of all those you have helped in the past ...

That may indeed be the problem. I am going to start over with my testing on Sat, when I have a little more time, and write down results as I go along. I think I can put power into the circuit at the first thing in the engine compartment ( unplug the AC Relay, put 12V toward downsteam side of plug) and get some good test data downstream from that. At least I could eliminate part of the circuit being a problem that way. I did get a good suggestion re a possible relay problem in the controller, but I'm not chasing that until I am sure all the downstream stuff works correctly. Thanks for the help!

 

[bobflood]

OK... that's helps the "clarity" maybe... and "I see says the blind man". It would appear that perhaps you are not getting "stable" voltage out of your controller.... which is quite possible. Have you "dropped" it and taken a look inside to see any obvious "burns / cracks / etc" that might be a clue? Sounds like you might be in the "broken controller camps" of all those you have helped in the past ...

budwich: Thanks for the encouragement. Turns out it was the EATC unit; another person on forum pointed me toward a bad solder joint on circuit board in EATC, and fixing it cured problem. My original testing process with a meter showed a positive voltage coming from the passanger compartment, so I thought my problem was downstream. However, when I went back with a 12V test light it would not light up - must have gotten enough "leakage" out of the controller to get a voltage reading, but not enough corresponding current to do any work. Lesson learned - a voltage reading by itself is not enough to prove a circuit good!