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a/c intermittent problems

dunbad

NAXJA Forum User
Location
uk
Hi,
After replacing my a/c pump and having a recharge by the a/c van man, It appears that when my engine heats up, the a/c stops working??!! On a cold start the a/c works fine and the clutch engages as it should, but after ten minutes or so it cuts out and the clutch stops spinning?
This kinda confused the mechanic whom didnt have too much experience of jeeps, and after he checked it over, he came to the conclusion that he had found the problem.
The mechanic stated that the pump works like a big magnet and the pump works fine when the engine is cold, but when it gets heated up they seperate too far hence making it not work. He states that the cure would be to remove the shims in the compressor to close this gap enough to make it work hot or cold? Does this make any sense to any of you or do you suspect something else?
many thanks
(its a 99 4ltr)
 
I think you need a better mechanic. Is the compressor clutch getting power? If its getting power and not engaging its the clutch. If its not getting power then the problem is elsewhere.
 
This is the weird part,
it gets power initially but then its as if the coil just stops working once the engine is warmed up? the pump is from a breakers but comes with a 3 month warranty and it appears ok. My last pump broke up on the pulley bearing and started making a nasty noise,
either way do you think that the mechanic has this wrong
 
sometimes when hot, the compessor clutch requires more amperage to engage. it sounds like the clutch is bad. you can have it replaced without even evacuating the system. however i have seen it where the clutch cost as much as a complete compressor
 
Hi,
Ive spent hours reading up on a/c problems but now im probably more confused so have a couple of questions .
First ive discovered that when turning my a/c on from a cold engine, it appears that the electric fan and the clutch on the compressor kick in as they should and i get cold air. But after about 40 seconds or so the electirc fan and the compressor clutch turn off for about 5 seconds. Then they start again for another 40 seconds or so and its repeated. (on for 40 secs, off for 5 etc.) But i get cold air the whole time and the evaporator and the pipes leading to it is like ice cold. Is this part normal?

second, after roughly 10 or 20 minutes i turn the engine off and turn it back on again, then i turn the a/c on, but all i get is the electric fan come on, but no clutch on the compressor, but the electric fan just stays on without cycling? The evaporator is no longer ice cold and the pipes leading to it just heat up pretty warm/hot.
Any ideas
thanks
 
Has anyone had "air gap" on there compressor?
I have read about it on other a/c forums which is what my technician says is most likely the problem, but never heard of this on a cherokee. Anyone had to remove any shims to reduce this gap?
many thanks
 
Did you transfer the clutch over from the old unit? If yuo did, then it does sound like maybe you didn't realize that the air gap needs to be checked. Usually though, too big of an air gap makes the clutch slip and burn up pretty quick - essentialy the same a riding the clutch on a manual tranny. The FSM says the gap should be 0.016 - 0.031". I can send you the picture of how to check it, but its basically just sliding a feeler gauge in the gap.

When you're having the problem, can you apply 12-volts to the compressor clutch and hear it engage and does it draw any current? FSM says 2-3.7 amps is normal.
 
Hi
The clutch was NOT transferred over from my last unit. And sorry i cant help answer any of the above two questions that have been asked as im backwards when it comes to mechanics. However it has now been fixed by the a/c technician (whos an a/c specialist)so ill try and explain what was going wrong and how he fixed it.

First on fitting the compressor everything worked as it should as explained above. Then when it stopped working he couldnt work it out. Apparently pressures were all good, and he checked out voltages pretty much everywhere but just couldnt work it out. He felt sure it was the shim needed removing, but on gently and very carefully tapping the clutch it still didnt engage which was confusing him. I then ran out of time so had to take the vehicle.

It was then that i noticed that sometimes my a/c would cycle and sometimes it would not. Either way, after having my a/c on for roughly 20 minutes the clutch would just stop.

Today he had another look at it and said the gap appeared not too bad and shouldnt be causing an issue but couldnt think what else it could be. He removed a shim, and now its working fine, ive had it going all day:greensmok . with no issues and ice cold everytime. And that was all he done was remove a tiny shim at no extra charge.
 
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