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Need A/C Advice please

Zel94XJ

NAXJA Forum User
Location
Orlando
Ok here's the situation:

My Cherokee (1996 4.0L, 4x2, AW4 Auto, 138k)

At one point earlier this year my A/C worked ok but not great. One day i flicked the A/C on heard the click or the compressor coming on then after 5 minutes the compressor clicked off not to turn on again for the entire trip. The next morning I came out started the car to drive to work and the same thing happened, after 5 minutes more or less the a/c clicks off not to turn on again for a few hours.

After searching this site I found someone else with the same problem though they didn't post if they solved it or not. here the link:

http://www.naxja.org/forum/showthread.php?t=1037000

***I did msg the OP in that post but have not gotten a response yet***

I decided to place a gauge on the low port (don't have a gauge that will connect to high port) and track the pressure as the A/C went from cold start A/C on to A/C shutting down. Ambient temp in my garage during test (89 +/- 3 because of the fans)

Engine off - A/C off = 75psi
Engine on - A/C off = 75psi
Engine on - A/C on = 35 (peaked at 47 then leveled out to 35)
Engine on -A/C fail = 40 psi (would likely head back up to 75)

At one point the low pressure was well above 50 psi but I let a bit of gas out to lower the pressure. (the gas release was less than 1.5 seconds worth when i pressed the valve in the fitting)

I jumped the clutch wire to + 12v and the clutch engages hot or cold. I jumped the switch connected dryer (i think) below the compressor and it didn't change anything. I also removed the shims behind the magnetic plate. The compressor pulley spins cleanly and the compressor spins with out snags. When the clutch is activated the cabin temp is quite cold.

So my questions are:

Where are the High & Low pressure switches for sure on the 1996?
If this is a heat related problem where do i start?
Any new ideas it's hella hot in central florida and A/C is important to me.
 
*update* After allowing the engine to cool an hour i get the same result. Compressor on for 5 minutes then nothing.
 
Clutch is on its way out. Try tapping the clutch with it running and see if it engages. Fought the same thing with the GF's 01 XJ
 
Without having the gauges to monitor both the high and low sides it's difficult to tell if the pressure switch is the issue. Go to autozone and you can borrow an A/C manifold for free (provided you put down a deposit). I'm sure the other chains have them as well I just don't happen to go there.

That said, I'd doubt that the pressure switch is the issue, like chpmnsws6 I'd lean towards a partially functioning clutch.
 
my clutch would function partially on my 98 exactly as you described. I pulled the clutch to remove a shim and found the back of the clutch to be corroded with rust. I sanded it off and cleaned it up and replaced with locktite and the AC has worked perfectly ever since. It's worth checking since it's a 10 minute free fix if that's the problem.
 
I went to junk yard and pulled the compressor front plate from a 95 XJ. I pulled my magnetic plate and it was corroded on the back. I cleaned the new plate from the yard and installed it with only 1 shim and the air gap seemed perfect according to sandens pdf manual. there was no change. 5 minutes on then nothing.

I did blow compressed air to clean the area behind the magnetic plate and lots rust or clutch dust blew out from between the pulley and the clutch. I am leaning towards the clutch now but i don't see how low clutch friction material and a 5 minute run time are connected. Please shed some light on this someone.
 
I was back probing the the electrical connector and noticed that when the Compressor clutch quits the V+ drops to 0. I am now thinking it maybe one of the pressure switches. Where are the high and low pressure switches? There is one on the evap canister newar the alternator. Where is the other switch on a 96 2x4 4.0 aw4 Cherokee?

The reason i think the clutch is fine is because if after it cuts out I jump the power directly to the batter the clutch engages. SO i know its not a mechanical problem. Thanks for the help.
 
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