The A/C in my 2000 4.0 liter XJ stopped working last week. It was working fine, then started blowing warm air while I was driving. When I got home, I checked and found the A/C compressor clutch was not engaging.

I remembered I had a problem with the A/C in my 2007 Cherokee years ago and replacing the low pressure/clutch cycling switch resolved the problem. So, last weekend I installed a new switch and the A/C worked perfectly. For one day. Then the A/C clutch again failed to engage. When I used a wire to jump the two switch connectors, the A/C clutch engaged and the A/C worked fine.

I returned the switch and got another. When I installed it, same thing. The A/C compressor will not engage. If I install a jumper wire on the connector, it works fine.

I admit these were Chinese A/C switches from O'Reilly, but that's all I could find locally. Did one go bad after a day and the other simply not work? Or, is something else going on?

Thanks.

 

Here's a description of your AC system functions and a schematic showing the functions of the switches.


Your Dual Function AC High Pressure Switch may be defective.

 

Today I finally got the A/C in my XJ working. In case anyone is interested, here's what it took:

- Replaced low pressure switch. A/C worked fine for one day, then the compressor wouldn't engage. Compressor would engage when I put a jumper wire on the low pressure switch connector.

- Tried multiple low pressure switches, same results.

- Bought a large can of "Arctic Freeze" R134 refrigerant. It comes with a pressure gauge that has numbers and not just color codes.

- Connected the Arctic Freeze can, but again the compressor wouldn't engage.

- Installed the jumper wire on the low pressure switch connector again. Compressor would engage, but only for a few seconds at a time.

- The gauge showed the A/C system was very low on refrigerant. I was able to charge it a little at a time with the compressor cycling on and off.

- Once the system had a full charge, the A/C compressor stayed on; even after I removed the jumper wire and reconnected the low pressure switch.

- Took the Jeep for a test drive. The A/C worked for a few minutes, then stopped.

- Could not get the A/C compressor to engage at all.

- Reattached the Arctic Freeze gauge which showed the system was still charged. No sign of leaks anywhere.

- Removed the A/C clutch. It had one shim behind it. I removed the shim and reinstalled the A/C clutch.

- Started the engine, turned on the A/C and the compressor engaged immediately. Let it idle for a while and the compressor stayed engaged.

- Took the Jeep for a test drive. A/C kept working just fine.

- Let it idle in the driveway a while. A/C compressor cycles off for a few seconds every once in a while, but otherwise stays engaged. The auxiliary fan kicks on when the coolant temp gets just over 210, then kicks off again. (I think this is how it's supposed to work in a 2001 XJ.)

So, I think it was a combination of:

- Bad low pressure switch
- Low on refrigerant
- A/C clutch is getting old and worn. It would engage, but when it got hot, it would disengage and not work again until it cooled. Removing the shim appears to have fixed that problem.

FYI, my 2001 XJ has a 4.0 liter engine with about 116,000 miles on it.

 

hey guys, is this the same schematic for a 98? thanks