For the last week I've had a problem w/ my air conditioning (A/C). One minute it will work the next it won't (Defrost also.. humid air). I did some trouble shooting... the pressure level is good.. the blend doors and all work.. what I found was the clutch to the A/C was not engaging when it is supposed to.. even when on defrost not A/C. Intermittent at best (it will all of a sudden decide to engage and I have Cold air and it seems to work fine next minute or ten, it don't). I replaced the pressure cycling switch it didn't help. I noticed that there is a rust colored / discoloration on and around the clutch on the A/C compressor.( no oil leakage) I am assuming at this point I have a bad clutch coil and or clutch.. how hard is it to replace myself.. I believe the compressor is fine .. no noise belts squeeling etc. and plenty of cold air once it is engaged. any help is apreciated.. my serp. belt needs replacing anyway. 110,000 miles. thanks, Jeff

P.S. 2002 Ranger 4X4 4.0 L SOHC

 

You may have a worn out brush on the clutch. The brush is the path for the electricity to engage the electric clutch. They push up against the backside of the clutch pulley. Trace the wire back from the compressor to a connector, and check for electricity. If you have volts to there, it is the clutch or the brush, or the backside of the clutch where the brush rides is dirty.
tom

 

OK, here's the deal.. I removed the connection to the coil and started the truck set the A/C to max and then checked the voltage at the connector. The voltage read 0.00 for about 3 min. (I thought I was having bad connect to the volt meter) but then all of a sudden it started floating anywhere from o - 9 volts, then just jumped to 14 and stayed there. I put the connector back on the coil and the Clutch immediatly started. I turned the A/C off inside the truck and then back on, The clutch did not reengage, so with the truck running and A/C on I checked the voltage again .. it was 0.00 then after about 5 -10 min. it showed power again floating to start. Is there another sensor i.e Ambiant air temp. etc. or relay that might be bad and where are they located? At this point I'm confident the compressor, clutch and freon levels are all good. anything else you can think of for me to try?

 

Which compressor clutches have brushes? All I have seen are simple electro-magnets, but then I haven't seen everything. jd

Normal operation is for the cycling switch to start stop the a/c relay when the pressure drops/rises to certain levels. There is also a high pressure switch which will shut off the circuit if the pressure is too high. There is also a wide open throttle relay, which shuts off the compressor during wot operation. I would check the pressures, and if they are ok, check voltages to the relay, and if they are ok, change the compressor relay. jd

 

interesting note! i was taking my son home today and it is warm outside ac on and no cold air.. soon after the ac came on.. then I had to pass a car .. full throttle.. ac went off.. stayed off .. then after dropping him off i was getting really annoyed at having no ac so i started really turning the temp control **** hot to cold profusly, leaving it on cold.. low and behold the ac stayed on all the way home.. 30 min. there has to be something else beside the obviose.. is there a temp sensor in the cab, bad selector switch ( although it didn't work on defrost the other morn.) humid air made it worse. and to reply to the last.. it is a coil which operates an electro-magnet to pull the cluth in..

 

Where is the compressor relay located? and where can I get one?

 

Have you jumpered across the low pressure cutout switch on the accumulator? It cuts out the compressor when the pressure inside the evap would cause icing to occur, and then re-applies as the pressure rises.
You have an intermittent connection being made, obviously. The control head A/C switch is an on/off, and the temp is controlled by varying the blend of air inside the plenum, at least for most. That means you should not be getting 'floating' voltage from the switch. But you could, if the switch is bad. You could from the WOT switch, and from the low cutout, or HPCO switch on the compressor head.
The HPCO is designed to cut the clutch when the pressure inside the system raises above a specific measure. It prevents over-pressure and leakage of refrigerant out the relief valve. Lots of switches, eh?
tom

 

No, I haven't jumpered that switch, YET! Yeh lots of switches. I replaced that one though, and after the clutch and compressor were engaged the pressure was right where it was supposed to be (acording to the gauge), and it abviosly isn't cycling as if it were low on freon. It seems to be a hit miss thing like a relay or something doesn't know it's supposed to be calling for the compressor or isn't totally engaging even though it knows it is supposed to. I can hear the blend doors rotate back and forth as i turn the temp. control **** in the cab.. I don't believe that is the problem.. hot air when i call for it..even with the control **** on defrost i got extreemly humid outside air .. fogged up the windshield worse than it was.. It has to be a sensor, relay somewhere that's not working right (DUH). Where is the control head A/C switch and where can I get one. RockAuto.com don't list it nor Autozone, unless it goes by a different name. what reads the temp. for it to blend air? The HPOC is located right on the compressor ? I can order that one. I haven't seen the WOT switch located it a parts available list anywhere yet either. and as for yesturday it stayed on for actually quite some time without kicking out.. i.e. low pressure KO/cycling switch. It has no chance to freeze up or possibly be cold enough to freeze unless there is a faulty sensor thinking it it frozen. I'm Clueless.. But don't have the money to take it in.. especially w/ winter coming on..although I know Defrost uses the Compressor also.