Thread: 1998 Jeep Cherokee AC Trouble

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Please help, ACs are my arch enemy. I've studied the system in school but on cars they seem to get me in trouble. Problem: My 1998 Jeep Cherokee straight 6, AC worked all summer, I have added nothing. I have not touched it. This morning no AC. Clutch is not spinning. Fuse Good. Relay good. Put gauge on low pressure side and the needle pegged into the red. This is all I currently know. Thanks for the support.

My guess is that you have a leak, maybe a slow leak, and it got to the point that your static system pressure is not picking up the pressure switch which is interlocked with the clutch. "Pegged into the red" was low, correct? You might get by with a can of refrigerant that has a stop leak included. Most of them come with an integral pressure gauge now days....

Its about 90 degrees out. When the car is off the low side pegs the needle (the needle reads 120 psi tops). The High side is reading 150 psi. The low side is pegging when the car is on as well. Should I jump the low side pressure switch when adding coolant?

That's a 134a system, so at 90F your low side should be 45 to 55psig and the high side should be 250 to 270psig. Having LP side high, and HP side low points to the system needing service, likely a bad compressor. Don't attempt to add refrigerant with your LP side more than double the normal value. You could blow up a can of refrigerant. Some charts to help - https://www.google.com/search?q=auto...kWy7lWHSnhI%3D

You have enough pressure in the system to operate the switch. Jump the switch and see if it comes on, if so run it for a few minutes (2-5) and see what the gauges read. May have a bad switch or clutch.

Yeah, 36 sedan's right, the system pressures are with the system on, compressor running, not static. Gotta get that clutch engaged....

Thanks for all the posts. I had to go to my four year olds friends birthday party so I was away. The compressor is getting 12v with nothing jumped. I jumped the low side and nothing (meant getting 12V, nothing wrong). Yeah, I'm betting compressor also. Thanks for the support!

Could just be a bad clutch. A jumper wire from the positive battery terminal to the connector should tell the tale on the clutch. 12V should pull it in solid.

The clutch is grounded through the brackets, sometimes a little corrosion will insulate the ground. You can run a jumper from a known good ground to the compressor. If the ground jumper makes it work, loosen clean and re tighten the bolts to the compressor.

Replaced the compressor. 30 minute vacuum then added coolant. The compressor did not kick on until I connected the high pressure gauge to the high pressure side and then removed the gauge causing a pusshhhhh sound as coolant was released. The compressor came on, I charged the system, and all is well. I am wondering now if the high pressure sensor had been stuck the entire time? Thanks again for everyone's support.

My neighbor said his AC quit working two weeks ago. When he disconnect the high pressure gauge from the system the same thing happened and his AC starting working again as with mine. No troubles he said for two weeks now.

The pressure switch is not a valve, just a port for the switch similar to a gauge. You had said you were getting 12 volt to the clutch which ruled out a bad switch. The shraider valve for the gauges is just a port valve and does not effect the systems operation. The pissssst is just the coolant escaping while removing the gauge hose. Always a good idea to push the hose towards the port while unscrewing the hose to minimize coolant escape, and be careful as the liguid coolant can freeze skin and seriously damage eyes.
The compressor has valves in it that if in the right position could prevent coolant gas from passing, and the evaporator will have some sort of restrictor / valve to lower the liquid lines pressure which could under certain circumstances prevent gas from passing (though there is usually a bypass here to equalize pressures when the system turns off).
It is possible that the coolant liquid locked the compressor momentarily (compressor is designed to pump gas not liquid), causing the delayed start (though this would cause the belt to slip and squeal), or the liquid had not converted to gas yet as static (not pumped up into pressure) liquid coolant can have less pressure than gas and not activating the switch at first. And, it is possible that removing the high pressure hose jarred a bad connection at the clutch wire.
I would check the clutch wire, if ok, let it go as maybe one of the other causes which fixed themselves.
Sorry for taking the long road.