Amnesiac

First of all, let me thank everyone for all their great contributions to this forum. So far I have been able to replace my track bar, steering damper, fix my rear hatch, and replace all the sway bar bushings because of the excellent information available here!

I have an '01 Cherokee Sport and the AC won't blow cold air. I have tried recharging with new R134, but even with the right pressure and the AC on max cool the compressor won't cut on. Also, when I remove the hose from the low pressure valve it leaks rapidly. I'm assuming this valve should hold the pressure even without the cap on.

My question is, is there anything simple I can do to troubleshoot this further myself? I have no experience working on AC units and I really have no clue where to start (well after trying to put in coolant that is). I have read in some places it takes coolant for the compressor to cut on and I am assuming I've gotten it up to the right PSI (I went as high as 30 and it's about 65 outside today) and the compressor just never engages.

Should I just throw in the towel and take it to a shop or can I try something at home to narrow down the problem? I'll add that even though the compressor doesn't kick on, the engine RPM does rise very slightly (100 or so revs) when I kick on the AC.

Thanks again for all your help!

rrich

Check the clutch to make sure it works.
Disconnect the connector at the clutch, then run a jumper to put 12 volts on the clutch. It should engage.
If it does, it's the wiring to it.
Swap the AC relay with another identical relay to see if it works then.
Let us know what happens, we'll go from there.

djb383

Sounds like the low side valve is loose or bad. The plastic caps are only dust covers and not meant to hold pressure. A/c can be tricky, let a pro diagnose.

Amnesiac

I do think the low side valve is bad. Sometimes I could remove the hose and it would hold the pressure, other times it would just vent it all out straight away. I bought a valve repair kit from Advance, but the valve in the kit is too small for the valve in the XJ now so I'll just return that.

I've been reading about jumping the clutch and I had a question about that, it sounds like I can jump a low pressure switch near the receiver, is this the easiest way to force the clutch to engage? I'm not even sure exactly what I'm looking for... I've also read where you can somehow jump inside the fusebox on other cars.

I actually bought a new relay for $12 to see if that would make a difference and it didn't, so I figure it's time to try to force the clutch to engage and if I can't get that to work I'll just take it to a shop.

Thanks again for all your help!

bev4ns

I think those valves should the same as in a tire valve. You can get a little tool at a parts store on the cheap and put a new valve stem in to fix that. They just thread in.

Just read your last post, sorry. Disregard the above statement.

My compressor wasn't engaging when I first got my XJ a little while back, so I assumed the worst. I filled it up with refrigerant to the max side of the "green" on the pressure gauge but still nothing. I then read further that those plastic gauges that come with the recharge kits are crap, so I added one more can for S's and G's. Voila: compressor kicks on and I have A/C. Not trying to point out the obvious, but when you recharged it did you have the A/C on and blowing at full? I don't really know much about it, but just my $0.02 as I just went through this myself. Good luck, hope you get it working!

djb383

There's an elec. connector on top of the dryer.....unplug it and run a jumper wire in the connector.

Amnesiac

I did have the AC on max cool, I even tried switching it around to some different fan settings and stuff to see if it mattered. I was filling it to recommended pressure on the cheap gauge on the refill kit from the parts store. I'm sure the gauge is no good, but I don't know if I feel up to just pumping it full of coolant to see if that kicks the compressor on. I'm not really sure if that's safe or if it would just be a waste of coolant.

I'll try seeing if I can jump the wire from the top of the drier and see if the clutch kicks on. If it does, I'll try to find out what I need to get to replace the valve and then I guess I would jump the compressor again and fill it with coolant with the compressor running and the engine on / max cool AC?

bev4ns

I think another easy troubleshooting step could be to just throw another can into it, but a can with the dye. Then you could see if there are any significant leaks causing you to lose pressure too fast to keep the compressor from kicking on. Just something super simple to try.

RTorrez1

Before you try to put another can of refrigerant in pick up a pressure gauge or just go to the auto parts store and barrow one from them. You don't want to over fill the system. You can cause more problems and it's not safe for you.
Try jumping it first and check the pressure before you move on.
Keep us posted and good luck.

bev4ns

Definitely check the pressure with a "real" gauge before you try the dye. Sorry, should have added that.

RTorrez1

That is why it's nice to come on here for help. You can get everyones input.

rrich

AC work was a fairly large part of our business.

1 - jumper 12 volts to the clutch to make sure it works, don't leave it on for long. That tests the clutch itself.

2 - If OK, and you've already replaced the relay, then -
3- disconnect the connector on the pressure switch on the drier. Squeeze the rubber connector to take it off. Jumper the 2 wires together in that connector. If it turns on the clutch it's probably just low on refrigerant. Don't let it run for long.

Replace that leaky Schrader valve where the hose connects - it's not the same as a tire valve, just looks similar. Real parts houses have the valve. Autochina doesn't. Also get the proper tool to remove/replace it, - it's different than a tire valve tool - longer.
Someone may have used a tire valve in it - garanteed leak!

Recharge - jumper the pressure switch to make the compressor run to help get it in. 3 12 oz cans max.
After 2 cans, try reconnecting the pressure switch to see if it runs.
If it runs, - it should now - put a thermometer in a dash vent. Close windows, fan on high.
Note the temp. Add a little at a time while watching the temp. As you add you'll notice it gets colder and colder, then starts going back up = STOP then. It's full. Your total will probably be 2 1/2 cans.

Amnesiac

Thanks for all the great tips everyone! I got the valve replaced and it's definitely holding pressure now. I charged it up to 55 PSI (compressor isn't cycling still). I'm not sure if I should go any higher trying to get the compressor to engage. It did try to kick on for a second around 40 PSI.

One thing now when I turn the AC off the engine RPM drops suddenly and almost sounds like it's going to stall. Could there be a problem with the serpentine belt that might be messing the compressor clutch up? I really have very little knowledge of this system, but I've noticed the belt is cracked and there's a ticking sound coming from around the belt.

I was going to try jumping the clutch to force it to engage, but I really don't know exactly what I'm doing so I figured I'd just try putting in a little more coolant with a good valve and hope I could safely get the pressure to where it would engage on its own.

djb383

Seems like there's a sticker under the hood somewhere that states a specific number of ozs of refrigerant.

JeepCoMJ

I, for one, am pretty confused by this. any "hose" removed from the system results in a discharge.


are you trying to say that you can remove the schraeder valve cap, and sometimes it holds, sometimes it doesn't?