Rusty2

Hey everyone! This newbe just bought a 99 Cherokee. Only issue I can find is that the Sandor A/C unit is not working. PO said the freon was checked and is fine. This may be wrong thinking, but before I take it to a tech or go purchase a recharge kit, I thought I'd try to check a few things myself. I have voltage to the fuses and the fuses check good. The dash blows air (just not cold), the aux. cooling fan engages when I turn on the a/c. The clutch for the compressor does not engage..... I would like to know how to determine if I have have voltage to engage the clutch. After reading many posts here, I tested and do have voltage at my low pressure switch and I put a jumper on it with no luck. Next I pulled the clutch, finding some rust and only one shim. I cleaned the rust off, put the one shim back in and since I needed the car, reassembled. Today I checked the ground that attaches at the clutch. It was good. Now for the stupid question... I see only one wire going to the compressor, but three coming out. One is the ground and the other two exit the compressor along side it. All three continue for six inches and then apparently two wires stop in side the wire loom with only one wire continuing on. What am I missing here. I'd rather not cut the wire loom. Aside from this little mystery, I'm hoping someone can tell me how to verify that power IS reaching all the way to the compressor. If I determine that it is, I guess I'll concentrate on the gap at the clutch plate. I'd also like to know how to test the relay. I don't have another similar relay there that I can swap in. That would be too easy : ) Thanks for any suggestion!

CCKen

To test for voltage to the clutch uncouple the clutch connector and, using a voltmeter, touch the pin/cavity with the meter + probe while touching the battery negative post with the - probe. Start the Jeep and activate the AC. You should have 12 volts at the connector. If not, Jumper the Low Pressure switch then the high pressure switch connectors. If no help, change the relay.

The clutch circuit is an odd duck. It has a diode between the Power and Ground wires in the loom. See pic.

Open this link.


https://www.cherokeeforum.com/g/picture/3583262

Rusty2

Ken! Thanks!!!! Your link answered my question about the wires coming from the compressor. I also did what you said And found that I do have voltage going in. Now I just have to determine why that voltage is unable to engage the clutch?
Clutch air gap maybe? Looks like I need a 90deg. wire feeler gage to check that with out removing the pulley. Does that sound correct? I think I have one some where. Any more suggestions?
Thanks again!!

Rusty2

So then,,,,, must I remove the pulley to check the clutch gap? The Sanden service manual indicates that I should be able to check this with a flat blade feeler, but it appears to recess inside the pulley just a bit. I think I'm getting a gap reading by sneaking in a 90deg. wire gage feeler with the pulley on. Does this sound right? On my wife's car I can check this gap with the pulley on using a flat blade feeler. Hmmmmm.

CCKen

Clutch gap has nothing to do with the clutch electrically engaging.


The clutch itself may be defective.


You can test the integrity of the clutch using an Ohmmeter.


The pic below shows me bench checking the clutch but it can be done insitu. With the meter - probe to the ground screw on the compressor and the meter + probe to the pin in the compressor connector.


You should see between 9.0 and 10.5 Ohms by checking the wiring between the clutch connector and the ground on the compressor.


If you see Open or some high resistance the clutch is bad.

Rusty2

CCKen, thank you so much for walking me through this. While I awaited your response, I removed the only shim. Bam! ice cold air!!! I mean super ice cold! I still think my gap is too large and the Clutch piece that I removed to access the shim is still pretty rough even after I wire wheeled it. Should I worry about any of that?
Thanks again for the advice! I saw through all your posts that you have helped lots of us here. Maybe the money you saved me can now be spent on Jeep toys and maybe I can help someone else with what I've learned
Rusty

CCKen

Not so fast with 'toys'. You ain't seen nothing yet with troubles that will cost you $$. Save your money.


Glad you figured it out.

Rusty2

Ya, I'm new to this forum, but this is my third Jeep. Drove the last one, a 1964 CJ for the last 17 years, but honestly that was one very dependable rig. I hope the cherokee will be as good and so far we're getting along real well!