Air conditioning not really working

So now that the warm weather is here, my A/C doesn't seem to be working very well. On warm days it works a little, but on really hot days it doesn't work at all. Any suggestions as to where I should start my troubleshooting?

Thanks!

Edit: forgot to mention it's a 99, 4.0L, auto.

Sounds like your low on freeon. And if low you have a leak in your a/c system. Take it in and have it recharge and dye added to find the leak. fyi you must be certified to work on a/c system. good luck

Get a refill kit from wallyworld and throw a can of refridgerant in there. At least half the time, you'll be good to go for another year. Never heard that you need to be certified for that.

So I charged it up and it blew nice cold air. I took it for a drive and after about 5 minutes I started getting the warm humid air. I had to go into a store for about 30 mins. When I got going again it blew nice cold air for about 5 mins and then the warm humid stuff again.

Any suggestions?

X2 on adding the dye. You probably have a leak. My guess would be the evaporator. A LOT of chryco evaps go bad. Once you add the dye (and run it for a while) take a look at the little black rubber drain hose on the passenger side of the firewall (about 3 inches long) for the evaporator. I'll bet you will find green dyed water dripping out of there.
If not, look around with a UV light and find where the leak is

So a leak would cause it to only work for 5 minutes at a time? It's still working fine whenever I start it up, but after 5 minutes it stops blowing cold air. I went looking for the dye the other night but the store was sold out. We had a few days of really hot weather last week so I guess everyone was doing what I was doing - trying to get their A/C working.

searchingforXJ said:

So a leak would cause it to only work for 5 minutes at a time?

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It's possible. Depends on how large the leak is. You may have had a leak that you charged up 'just enough' to get it to work. What happens is as the thing runs, the pressure on the low side goes down too low, causing the compressor to cut out. That 'may' take 5 minutes of running to get the low side pressure low enough.
What then happens, since the compressor is not running, the pressure in the low side builds up enough to let the compressor cut back on. It will then stay on for ~3-10 seconds or so, then cut back out.
The easiest thing to do is put the air on and look under the hood and see what the compressor is doing. If you see the clutch engage, then disengage shortly thereafter, then re-engage, I would say you have a leak and are still low on 'freon'. The best thing to do would be to hook up a set of gauges to see what exactly is happening in the pressure department, as is is possible to over fill the system, which is not exactly safe and an overfilled system does not run as efficiently as it should either.

I suggest converting it to OBA!

Is you compressor running when the warm air is blowing? I had a similar problem and found the clutch was not always activating. Ended up being too large a gap in the clutch. Spacer change fixed it. BTW: I lived with it for 2 years before I figured it out! I was replacing and evacuating, replaced the coil and looked at $500 compressors but couldn't get past the second zero!

I work on almost all periperals on my XJ but air conditioning can be a bit tricky so I trust that one to the guys certified and with the right equipment (gauges, leak detectors, etc) to troubleshoot it.....

i will probably just end up taking it to a shop, I just have absolutely no confidence in any of the local shops. The stealership has a bunch of idiots that will just want to replace part after part until they get lucky and get it working, and the other shops in my area tend to nickel and dime you to death. it just doesn't seem like anyone is interested in doing an honest days work anymore.

Hold onto your wallet if its the evap !

I'm not putting any big money into so if it's not a simple fix, it's not getting fixed! It works for 5 minutes of every 20 right now so that will have to be good enough.

You should make sure the system is working after 5min. like someone above said after 5 min if the system seems to stop cooling pop the hood see if the compressor is working (if you cant hear or feel it in the cab) if it has stopped you may still be low on refrigerant. when you first run the system if you can do it in the driveway and when its cooling see if the low press line is very cold and at the accumulator/drier is sweating. is should be if its hot outside and if its humid it should sweat a lot.that's why you see water under the car on hot days lots of water is pulled from the air.in the case of the lines they are so cold they cause the moisture to condense on the line.like cold can of beer will sweat out in the heat. now if you don't see the low side line get very cold and sweat you should add more refrigerant. depending how low the system was? if you added just 1 can that may not have been enough. now if its cold and sweating then its working and after 5 min if you loose cooling check the system again if it running and the line is cold, if not its a internal issue like expansin valve or screen that needs service , if the low side line is still very cold you may have a duct problem in the dash or the vacuum system that controls it? maybe this info will help ya.

searchingforXJ said:

I'm not putting any big money into so if it's not a simple fix, it's not getting fixed! It works for 5 minutes of every 20 right now so that will have to be good enough.

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So I haven't had a chance to take it to a shop yet, but I did connect the pressure gauge that came with the refill kit while it was running. On the low pressure side when the A/C is blowing cold air it's around 38-40 PSI. When it stops working the low side goes up to 85 PSI. I would imagine there is a high pressure cut off switch somewhere, and when it jumps to 85 it cuts things off.

Any suggestions why the pressure jumps up like that?

sjx40250 said:

Is you compressor running when the warm air is blowing? I had a similar problem and found the clutch was not always activating. Ended up being too large a gap in the clutch. Spacer change fixed it. BTW: I lived with it for 2 years before I figured it out! I was replacing and evacuating, replaced the coil and looked at $500 compressors but couldn't get past the second zero!

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Did the same thing with mine about a week ago...only after taking it to a shop and getting a fresh recharge. It quit working 2 minutes after I picked it up. Jumped on when I got home and found this: http://www.sanden.com/images/SD_Service_Guide_Rev.2.pdf

Took some measurements of the air gap, determined it was out of spec. Pulled the one and only shim the next day. Been working great ever since.

gw204 said:

Did the same thing with mine about a week ago...only after taking it to a shop and getting a fresh recharge. It quit working 2 minutes after I picked it up. Jumped on when I got home and found this: http://www.sanden.com/images/SD_Service_Guide_Rev.2.pdf

Took some measurements of the air gap, determined it was out of spec. Pulled the one and only shim the next day. Been working great ever since.

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I went to try that after work today but couldn't get enough of a grip on anything to get the bolt off. Guess I need to go find the special tool for that.

I used the wrench that came with my Dewalt griner. It has two pins on the end to engage the holes in the nut that holds the discs on. Stuck one pin in one of the holes and just let the other jam up against one of the rivets (or whatever they are) sticking up.

gw204 said:

I used the wrench that came with my Dewalt griner. It has two pins on the end to engage the holes in the nut that holds the discs on. Stuck one pin in one of the holes and just let the other jam up against one of the rivets (or whatever they are) sticking up.

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Thanks for the tip, I'll try that.

Quick way to determine if the clutch is the culprit- when the compressor kicks off, see if it still has voltage at the clutch connector.