Hi.
My A/C stopped working one day. I troubleshot it with a meter (I am an EE).
Once I short the relay contacts the clutch will engage, which means, that the Low pressure switch and everythin that is in series with the clutch relay contact group is OK.
Now the relay coil is hooked up to 12V via some switches (possibly - for whatever reason Chilton sch for 92 does not show how the A/C hooked up so I use the similar sch for RENIX controller), and they are also OK, as when I hook up the ralay and Ground the GND coil pin - relay clicks.
WHich means that the GND path for the relay is not there. It is provided by the output of the ECM (the computer).

So, the computer gets the A/C requests from the "Cycle Switch" (the temp sensor, thermostat, or what you call it).

Which leaves two likely culprits: the ECM module and the thermostat switch.

Also, when choosing AC on the dashboard, I do not hear idle RPM going up (I think it should), which tells me there is no A/C request being processed.
Again, could be either switch or the ECM module.

Now what I do not know is this: I have zero idea where either one is located and how either one looks.

Chilton is not very helpful either. So if anyone can guide me where to find those ECM and thermostat switch, or anyone has a photo of them, or can descrine the exact procedure for Cherokee 92 (not Grand Cherokee - the regular Cherokee Laredo 92, inline 6, 4.0 Liters, 4 doors, 4x4) - I'd be eternally grateful.

Mike

Mike,

Your best bet is to drop $10 on a one-week subscription to eautorepair (Mitchell On Demand) and download the entire diagnostic procedure and all the wiring diagrams and component locations. Click here: Eautorepair

Rick,

Thanks a lot. I will give it a try.


Mike

Mike, Are you sure the system has good freon charge? If you've sprung a leak,compressor will not engage. Vern

Vernon

Thanks for answering.

I was able to procure the real Jeep Cherokee 92 schematics (Chilton/Hanes admitted they did not put the A/C clutch wiring in their manual for 92 model and sent me the extra pages); prior to this I use some 80-s models and they happen to have the Low Pressure switch in the contacts group of the clutch relay. So I was undre impression that the pressure was OK.

However the real schematic does show that for 92 Cherokee Lop Pressure switch is indeed in the Clutch Relay control coil circuit. So the fact that clutch does not engage does point to thet Low Freon Charge as the main possible culprit.

I plan visiting A/C shop soon to pinpoint the leak and re-charge the system.

There is also a gray ten pin connector on the located on the left fender shield that could be corroded or loose.

Attachment 8943