Kscha41

Hello everyone. I just bought my own 01 cherokee after working on my friends 00 for years and I fell in love with one and had to find my own. So I found a 01 with 215,000 miles on it for cheap. It had motor problems but I fixed those. My new problem is the a/c. It doesn't get cold. The compressor kicks in when you turn it on and will continue to run without a problem. But it doesn't blow cold air. Next thing I did was hooked up my gauges to the low and high side. With everything off both the low and high was about 85 psi and when I turned the compressor on both the low and high never changed from 85 psi. So I assume that's why I am not getting cold air. But does anyone know why the psi is not changing when the compressor is turned on? I know the low normally drops and the high normally rises when turned on. Oh btw the compressor looks like a reman according to the sticker. Sorry for the long post and thanks for any help.

Jose.Aviles15

The compressor is not "compressing".
When the compressor is operating it brings down the low side pressure to around 30 to 40 and compresses the refrigerant to 200 or 250 on the high side. That's just approximate, RPM, ambient air temperature, Blower speed and condenser condition are all key factors.

It could be the reed valves inside the compressor or the pistons themselves. Valves need to open to create suction and close to compress and increase pressure.
Send the high pressured refrigerant through a small restriction and you create a pressure drop. A drop in pressure = Drop in temperature. Which is why you are not getting cold air. You have no pressure drop.

Replace the compressor, orifice tube, and dryer. If the O-rings have a square appearance buy an o-ring kit and replace them all. *note when replacing dryer make it the last item installed with the least amount of time exposed to the air. Once everything is installed apply vacuum for 30 - 45 minutes. *to remove moisture from the system. I usually stop the vacuum and leave the gauges on to see if there is a leak. Guage will go from -28" to 0 if there is a leak.
Lastly charge system with the correct amount of refrigerant. Hint if the system stops sucking in the refrigerant before the full amount of refrigerant is achieved SHUT OFF the HIGH side valve and turn on vehicle and A/C so the compressor can take the rest of the charge.

Kscha41

Thanks for the great response. I was hoping for something a little cheaper and easier but I guess you don't get that with a jeep. 😁 According to the previous owner the a/c worked in the fall. I just don't want to have to dump a lot of money into something with this many miles. Thanks again for the great response.

Fred/N0AZZ

You might try one from a JY and hope its OK but once they sit for long periods unused, you know the story.

Kscha41

Thanks. I was also thinking this and will keep a eye out for a good used one next time I go to the junkyard.

Kscha41

Well after looking up the price of a new compressor I will definitely find a used one. And I figured what the heck it is already broken, maybe tapping on it with a hammer might free something up but I had no luck with that.

Knucklebuster

Before you start throwing money at it, check the electrical loop that turns the clutch on and off; high pressure cutoff switch, low pressure switch, relay and fuse for the clutch. All the info that you need is in the wealth of posts on Air Conditioning found with a search.

Kscha41

Thanks for the post. The clutch would turn on the old one but nothing would compress. Over the weekend I got a compressor out of the junkyard and installed it. I haven't really used it except for in the garage when I installed it. The one I just installed now changes the pressures on both the low and high side and it feels like it cools. I turned the old compressor over by hand when I took it out and it was not compressing any air unlike the jy one I just installed. I will have to wait till it warms up a little since it is now only 50 degrees today to give the new compressor a real test.

Knucklebuster

Sounds like you're on the right track. Before you run that compressor, i hope you pumped a vacuum on the system and put in R-134 with oil. Or have a shop evacuate and r-charge the system.

Kscha41

I did put oil in the system and then pulled a vacuum on it and then I recharged it. When we get some warmer weather I should be able to give it a real test.

Kscha41

A little update. I have used the ac the past couple of days and so far it is working great. But one thing I have noticed. The electric radiator fan does not turn on when the ac is on. It will turn on if the coolant gets warm if your idling or it will turn on if you unplug the harness at the coolant temp sensor. I am thinking that maybe it is the high pressure sensor. Does anyone else think it is that sensor and if it is, what is the technical term for that sensor so I know what to ask for at the store?

Bustedback

The electric fan on a 2001 XJ won't kick on until the A/C head pressure reaches 360psi, or when the coolant temp reaches 219 degrees.

Turbo X_J

You really don't want to charge the system with the high side valve open.

drhoward1988

Lol X2. I had a high side schrader stick open when I pulled the quick connect off. helluva suprise. system still running too. quite the party especially when you aren't expecting it

Kscha41

Ok. Thanks. I guess I will have to wait and see if it kicks on at some point.