'99 4.0L A/C Issues

I know, I know it's a Jeep and I should even bother with A/C but it's been so HOT here in Southeast that the A/C is a must.

I had the A/C charged last week on '99 and it will blow ice cold for about 30-45 mins. After which it slowly looses the chill to the point it's blowing out ambient temp air. Cut the Jeep off and let it sit for 30 mins and then A/C blows ice cold again.

Any ideas what could be causing this? :dunno:

Is the compressor kicking in?

Somewhere or other in my FSM there is a big A/C troubleshooting flowchart, I'll have to see if I can find it and walk you through it.

kastein said:

Is the compressor kicking in?

Somewhere or other in my FSM there is a big A/C troubleshooting flowchart, I'll have to see if I can find it and walk you through it.

Click to expand...

I've got a '99 XJ FSM, I didn't realize there was a troubleshooting flowchart for the A/C. I'll take a look tonight. Upon further research I'm hoping that a shim needs to be removed from the clutch.

Pretty sure there is, it might be in the body/chassis manual though. I've got the 6-volume set for my '98, so let me know if you can't find it.

Just checked, there is a very detailed checklist in the heating/ac section of the main volume. In my 98 manual the diag procedures/checklist start on page 24-10.

I have a 99, when my AC went I had the evaporator replaced, it's been 2 years and has been blowing like the Arctic ever since, I went one summer with no AC, that was no fun.

I believe they saved money by switching to the aluminum evaporators instead of copper at some point and they did not last.

It not a easy job you have to take out the dash to get to it, a real pain and its time consuming.


Good Luck

If it does blow cold, but warms up after it's running for a while then check the pressure. Too high pressure is just as bad as being too low. I'm guessing that you might be freezing up something, and it'll thaw out when it sits.

I haven't had A/C in my XJ since 2007. But I hope to replace the evaporator in 2 weeks during my vacation time. With the extreme heat the past few weeks here, I'm sooo glad I've got a car with working A/C I can drive.

Is there a very large puddle after it's parked when the AC quits?

Thanks guys for the help. I "think" that I got it fixed last night. It seems as though the gap in between the clutch plate and the compressor becomes excessive over time causing the clutch to release when the compressor gets warm. There are several guys on JF that are having the same problems. The fix for it is to remove the shim(s) that are behind the clutch thus closing the gap as well as sanding the contact surface on the clutch plate and the compressor. I did this last night so hopefully that fixed the problem and the clutch won't release anymore until the switch is turned off.

In answer to your other questions, yes there is a good size pool of water under the passenger side of the Jeep when running or turned off after running the A/C that drains from the evap core behind in the dash unit. I replace the evap core in my dash unit when I swapped everything from the XJ to the MJ as preventative maintenance.

let us know how that works out woodcrawler... I have the exact same problem with my 2001. drives me nuts! If your rollin down the highway it'll blow cold for longer. probably because the system can stay cooler.

steed76 said:

let us know how that works out woodcrawler... I have the exact same problem with my 2001. drives me nuts! If your rollin down the highway it'll blow cold for longer. probably because the system can stay cooler.

Click to expand...

Mine is the same way. When you are rolling down the hwy the compressor can stay cooler with the air flow. The theory is once the compressor heats up the electromagnet that holds the clutch to the compressor is not strong enough when the gap is excessive and the contact points are dirty.

Check out section 8.2.6 from the Sanden manual:
http://www.sanden.com/images/SD_Service_Guide_Rev.2.pdf

Also this thread on JF has a lot of good info and pics of the shim removal process - VERY EASY.

http://www.jeepforum.com/forum/f11/ac-issue-compressor-not-engaging-1064083/

Hope this helps.....waiting I'm answering my own questions....didn't I start this thread :wierd:

Update on my findings. First my syptoms were identical to woodcrawlers.. ice cold air for 10-15 min then like turning the heat on. If i let the system cool it would blow cold again. On the highway it would work half "assed" cool then ambient, back and forth just enough to be uncomfortable on a hot day. Tonight i removed the clutch, removed the 1 shim underneath it, cleaned(sanded) the clutch face and hub with my dremel lightly, and reassembled. This a/c system has never worked this well since i've owned the truck. it ran for 50 minutes sitting at idle ice cold. Then i drove it 30 miles without a hiccup.. i will say I ran to autozone and rented the clutch holder tool so i could easily remove the nut, and it made things very easy. On a 1-10 scale if difficulty its a 3. Remove the fan shroud with a 5/16 socket, 2 bolts.. then clutch tool, remove nut with a 14 mm socket and bam thats it... thanks everyone in this thread for the pics and stories. wish we could have a sticky thread about this concern.:rof:The clutch enguagement and disenguagement doesn't seem to put such a heavy drag on the engine anymore.. i can hardly tell it's running, which is another plus!

The symptoms you mention are typical for most late model XJ's....

It sounds like the low pressure switch has failed, which is what is causing your evaporator to ice up. Once it ice's up, air flow is impeded, and you get the luke warm air. Once the ice melts, you get the normal cool flow until the evaporator ice's up gain about 20 minutes later. The cycle repeats. A good clue is large amounts of water under your rig...that's the melted ice. You can easily replace the low pressure switch, that is located on top of the accumluator. You can remove it without losing charge, as there is a schraeder valve that keeps your refrigerant in check...just swap in a new one.

Just an update. We drove the Jeep today for 4+ hours at hwy speeds in 90*+ temps and the A/C blew ice cold the entire time. Hopefully this small trick will help others out.

great news woodcrawler!!! I have been driving mine all day, letting it idle in traffic, and operation has been flawless! Nice and cold.. about 41 degrees at the vent according to my vent thermometer at idle!!:clap: