Help troubleshooting A/C Compressor - JeepForum.com

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post #1 of 18 Old 05-27-2013, 01:27 PM Thread Starter
jrandallc
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Help troubleshooting A/C Compressor

2000 Grand Cherokee Laredo Inline 6

A/C has not been blowing cold lately. Before the cold finally died, I noticed that the A/C would not blow cold occasionally, but then it would kick in and work next time I drove it. I experienced this off/on (mostly on) behavior for about two weeks before the cold finally went away.

Current Symptoms:
*Compressor clutch will not engage
*With A/C on, I get voltage to the electrical connector at the compressor
*I can turn the clutch with a wrench to the front bolt, so it does not appear to be seized
*I checked Ohms on the A/C Pressure Switch and it measures a slight resistance, but it will not get to zero Ohms. This could indicate a pressure issue causing the clutch not to engage, but...
*If I jump the A/C pressure switch, the clutch still will Not engage.

With the resistance across the pressure switch, I was hoping a simple recharge may fix me, but it seems that since jumping the switch failed to engage the clutch, that would be a dead sign of a bad compressor. Is that the case, even though the clutch is not seized?

I have already checked the fuses and relays and they all appear to be fine.

Is there anything I've missed that I should check out before I break down and replace the compressor?


Last edited by jrandallc; 05-27-2013 at 01:38 PM.
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post #2 of 18 Old 05-27-2013, 01:42 PM
lazyWJ
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If you have voltage to the clutch, it could be your clutch is gone or out of adjustment. With the ac on and the engine running, rap the front of the clutch with a mallet or hammer handle and see if it engages. The air gap might be too large. If you remove the center bolt on the clutch, you can remove the clutch. Inside the back of the clutch there are some small washers you can remove or add to adjust the gap. If the gap is too big, the magnet won't pull it to engage, or it will only work intermittently.
If you don't follow what I'm saying, you can see it with the engine OFF. Push on the front of the clutch, it will move towards the back of the motor and feel "springy". That's how it engages. The coil in the clutch energizes and pulls it back far enough so that it rubs on the pulley and grabs it, engaging the compressor. This sounds like a clutch issue, not a compressor issue. Check this and let us know what you find.

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post #3 of 18 Old 05-27-2013, 05:17 PM
86cj74.2L
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Voltage to the clutch may mean nothing. The relay for the clutch probably or may be provide a ground.
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post #4 of 18 Old 05-27-2013, 05:25 PM Thread Starter
jrandallc
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LazyWJ, I'm going to put you in my will. The clutch was exactly the problem. It took a few taps to get it going, but now just one or two taps on the front will kick it in gear. Now I can get it repaired more directly. Thanks for the quick reply!
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post #5 of 18 Old 05-27-2013, 05:27 PM
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No problem, glad it worked! You can remove a washer or two from the back of the clutch and it should be fine. They tend to stick in the clutch so you have to whack it on a hard surface or use a pick to get them out. It's hard to explain but a 5 minute job to do. Good luck!

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post #6 of 18 Old 05-28-2013, 12:48 PM Thread Starter
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Thanks again, LazyWJ. I picked up a spare compressor at salvage this weekend for $35. I'll probably use it as a test subject to get familiar with doing this repair.

It seems like this repair could possibly be done without removing with compressor (and without having to drain the refridgerant). Is that a possibility?
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post #7 of 18 Old 05-28-2013, 12:52 PM
its-me-B
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i was having the same issue with the clutch not kicking on... tried hitting the clutch with a mallet and boom the clutch kicked on. but i don't have any cold air from any vents...
any thoughts?

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post #8 of 18 Old 05-28-2013, 01:14 PM Thread Starter
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its-me-B,

Simple thing first, just double check that the AC button is actually engaged on the console. It may have been accidentally hit.
After that, I would check the pressure on the low-side port on your system. You may need a recharge. I recharged my son's Taurus this weekend. He didn't realize how uncold it was blowing until I recharged it. His pressure was so low it was causing erratic behavior in his clutch and he said that sound went away as well. I noticed it too when I started recharging and the clutch behavior stabilized the closer his low-side pressure got to normal.

Others may have better advice, but that is where I would start.
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post #9 of 18 Old 05-28-2013, 01:23 PM
its-me-B
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yeah the ac was on... i might try recharging it this weekend.

Do the world a favor, hurt a honda...
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post #10 of 18 Old 05-28-2013, 01:31 PM
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Apply voltage and ground to clutch. It should move in (click).
You can check resistance between battery ground and each clutch pin.

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post #11 of 18 Old 05-28-2013, 02:36 PM
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There is a low psi pressure switch that prevents the clutch from pulling in when the system gets too low.
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post #12 of 18 Old 05-29-2013, 11:19 AM
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Quote:
Originally Posted by its-me-B View Post
i was having the same issue with the clutch not kicking on... tried hitting the clutch with a mallet and boom the clutch kicked on. but i don't have any cold air from any vents...
any thoughts?
Really need to check your high/low pressures. If your compressor runs steadily once you get it turning it's possible that the compressor is shot. If the charge is low it will cycle off especially if you rev the engine. If it never cycles off, it might not be "compressing".

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post #13 of 18 Old 06-29-2013, 08:25 PM Thread Starter
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I finally got around to removing a washer to adjust the width on my clutch and it seems to be engaging regularly without having to knock it since then. However, a different problem has come up. The clutch is cycling pretty frequently; about every five or six seconds. I assumed this had to do with low refrigerant but when I jumped the A/C low pressure switch, it didn't fix the problem. The A/C clutch still cycles frequently. I would have assumed that if it was just a low pressure/low refrigerant issue, jumping the switch would have resolved it. Also, jumping the switch (actually jumping the harness that connects to the switch, just to be clear) should effectively bypass a faulty switch, correct?

With the switch and pressure out of the picture, what else could be causing it to cycle on and off so rapidly?
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post #14 of 18 Old 06-29-2013, 08:45 PM
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Quote:
Originally Posted by jrandallc View Post

With the switch and pressure out of the picture, what else could be causing it to cycle on and off so rapidly?
Pressure too high will do that as well.
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post #15 of 18 Old 06-29-2013, 09:00 PM Thread Starter
jrandallc
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Thank you, narnwv. I'll take a closer look at the pressure. Is there a high pressure switch on the 2000 Grand Cherokee? I haven't been able to identify one.
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