The AC in my 96 Grand Cherokee, which was last charged in July 2020, had been working when last needed, but when I started the engine during a cold snap of 6 degrees below zero F several weeks ago, I heard a squeal from the engine and the AC pulley was smoking, even though I didn’t think the AC was turned on, and I shut it down. When the weather warmed up later, the AC pulley was seized and would not turn. I removed the clutch disk (scored), the pulley (had to use a puller to get it off the coil), and the coil (burned and stinking), and the compressor itself was seized. Yesterday my new compressor arrived and when I removed the old one (there was still pressure in the system), removed the valve body, and turned the compressor over, only enough oil to cover the very bottom of a measuring cup came out. The manual says to measure the oil in the old compressor and put the same amount in the new compressor, but that can’t be right in this case. A sticker on the new compressor says it has 8 ounces of PAG46 in it and I am not sure what to do. I don't need AC right now, but I have to install the new compressor so I can put the belt on to run the engine and move the Jeep. Any suggestions?

 

Until you find out how much oil it needs, put it on and leave the clutch unplugged. That way you'll have the pulley, but won't run the compressor. The A/C is designed to run in defrost to keep the system functioning and the seals lubricated even in the winter. The lack of oil in the original compressor is probably what caused it to seize. I would connect all the hoses with new seals as well to keep the system clean and keep moisture out, but don't charge it until you find out if 8oz is the right amount. Don't forget to pump it down it vacuum before you charge it though.

 

This is my tow vehicle, so I wanted it running in case something else breaks down. I don't use it as a daily driver and I disconnect the battery between uses. The new compressor is on now but electrically disconnected so it won't engage. I noted when I started it that the heater was still set on defrost and the AC snowflake was not on, but when I turned the heater off and back on the snowflake came on and I had to push the AC button to turn it back off. The AC apparently comes on automatically even if it was off when the battery was disconnected. I tried shutting it off again and when turned on the snowflake came on but it went out when the heater was turned to defrost. I suppose that when I started it in the cold, the AC probably came on until I turned it to defrost.

 

Whatever the lights do or don't do, as long as the compressor clutch is disconnected it won't run. What the whole rest of the circuit does is turn the compressor on and off by monitoring pressures at different places in the system. If you're concerned about it, pull the fuse.

 

Yes, I am aware that the clutch will not operate when disconnected. I was looking at the snowflake to determine if the AC had tried to come on when I started the engine in the below zero weather and I assume it did activate the clutch before I turned it to defrost. Perhaps it was just coincidence that the compressor seized up at that moment when it had been operating OK before. The odd thing was that at the time I saw the smoke from the center of the pulley I am pretty sure the pulley was still turning and the belt was not slipping, but later after I removed the belt the pulley was totally seized, both the pulley bearing and to the coil. I am still wondering if the unusually cold temperature was a factor.

 

The cold may have reduced the running clearance between the clutch disc and the coil making it stick and that resulted in it overheating and seizing, that's possible. Funny, now that you mention it, my WJ has 267K miles on it's original power steering pump. One morning when it was 5*F, the engine fired right up, but I couldn't move the steering wheel. it was like the lock was still set. Then there was a quick squeak and it loosened up, but it moaned when I turned the wheel. I think the pump was locked up and the belt slid until it got hot, then had enough torque to turn the pump. The steering box only has about 25K on it so I don't think it was that. The pump seems to be working fine now, but it's getting replaced soon.

My A/C hasn't worked in 8 years so when we replaced the engine I got a bypass pulley and removed the entire system, even the condenser. There is so much more room to work on it now. The reason I did that was I knew the evaporator was shot anyway but I couldn't afford to replace it when I did the heater core. We don't get that many days in the 90's around here that I need A/C. My dad says I still have the 4-60 A/C....4 windows down...60 mph!

 

Interesting about your PS pump in the cold. Before the AC compressor lock up, the last work I had to do on my ZJ was to replace the PS pump pulley and the radiator. I had just gotten home from a 150 mile trip to retrieve my 04 Mini cooper S JCW that had broken its belt tensioner (and trashed the belt and crank damper in the process) and as I was backing the trailer up to the barn the power steering quit working. I got out to see if I was in the right place and suddenly steam began pouring out from under the hood. Turned out the Chinese PS pulley had broken into pieces no longer turning the water pump and the original brass tank radiator blew a seam from the overheat pressure. Seems it is always something. Before that I had spent $250 in parts to replace the front rotors and calipers with a PowerStop kit because the front calipers kept sticking. Before that it was a failed computer that took two tries to find another one that would work. It is a good tow vehicle, though. Now if I could get the Overdrive lock out button to work It would be perfect; that button has not worked since the computer change.

 

Dorman or somebody makes an idler pulley that bolts on in place of the compressor. If you look you might still have a sticker for serpentine belt routing that shows a dotted line for how to run the new belt without a compressor. You have to change the belt as well.