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Old 02-26-2010, 10:18 PM   #1
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Question Wrangler A/C problem

Jeep pros. I need your help. I've had a problem with my 2002 Wrangler 4.0L for at least the past year. The a/c system stays on all the time. I disconnected the 3 knob control unit wiring except for the vac lines and the system still runs. With all wires connected to the 3 knob control unit and the selector switch set to Off, the system still runs, however the fan shuts down as expected. When I remove the a/c clutch relay in the relay box, the clutch disengages. Replacing the relay causes the clutch to reengage. I tried switching relays but that doesn't help. I think the relay gets a feed from the PCM unit. Could it be a software problem? help would be appreciated.

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Old 02-27-2010, 07:27 AM   #2
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I was just browsing the FSM and it may help you find the problem. PM me if you want it. Remind me of your year. It sounds like the relay is getting the signal to energize the clutch.

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Old 02-27-2010, 06:31 PM   #3
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I realize that the relay is getting a signal. It usually comes from the PCM unit.
The PCM unit is getting an ac request from someplace or its in the PCM itself.
I had the climate control unit completely disconnected except for the Vac lines. The clutch still cycled. It would even cycle with the climate control set at OFF.

Thanks for your reply.
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Old 02-27-2010, 06:33 PM   #4
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I have a 2002 Wrangler Sport 4.0L.
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Old 03-01-2010, 10:30 PM   #5
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Help! I can't get my ac system to shut down.
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Old 03-01-2010, 11:10 PM   #6
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i dont know how it is on here but on my car i had to unplug the plug that came out of the compressor on the motor. I dont know what harm that would do?
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Old 03-01-2010, 11:49 PM   #7
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Time to convert to on board air.
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Old 03-01-2010, 11:52 PM   #8
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May get a check engine light with code. I guess it's better than wearing out the clutch on the compressor. When the heat sets in here I can connect it back up.
Thanks for input.
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Old 03-02-2010, 12:11 AM   #9
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I found it alot easier just to pull the clutch relay. We'll see how it goes.
Once again, thanks for the help.
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Old 03-02-2010, 01:13 AM   #10
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Defrost will send an engage signal. Maybe the computer defaults to this mode if everything is unplugged. If you hook it all back up and it stays on, make sure the vent selector knob is working correctly. Might try to find another one in a junk yard. I put red led's in mine but I took the vent selector switch apart the wrong way. Now I have to gently select where I want the air coming from because I lost one of the ball bearings that help to STOP the switch in the desired locations. If I hit a big bump it will change selections and sometimes turns on the a/c
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Old 03-02-2010, 04:19 AM   #11
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I'm not 100% certain, but I think the connection to the PCM does not energize the relay - that connection is to tell the PCM to raise the idle a tad to compensate for the additional load of the AC.
Easy enough to tell - disconnect or cut the wire to the PCM. If the AC still runs, it shows that connection is an input to the PCM, not an output.


I'd start by disconnecting the HI/LO pressure switch - the clutch should disengage. Then measure the voltages back to the dash switch - I'd bet it is the dash AC/heater switch itself shorted inside. As you move the dash switch from AC to heat, the voltage to the HI/LO switch should go on and off.

If I'm not mistaken, the relay is energized by that dash switch (the coil), the power to engage the clutch comes from the HI/LO pressure switch.
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Old 03-02-2010, 04:32 PM   #12
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When I had the dash control system completely disconnected,except for the vac lines, shouldn't that have eliminated the short in the switch? The a/c still cycled. Maybe I have a short in the wires to the a/c-heat switch.
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Old 03-03-2010, 10:10 PM   #13
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I pulled the fuse on the clutch relay. Leaning towards buying a new climate control board. Looking towards getting better mileage until the heat kicks in.
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Old 03-04-2010, 09:04 PM   #14
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Ordered a new climate control panel today. Hope it works.
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Old 03-12-2010, 01:15 AM   #15
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Put the new climate control in. Same problem. Traced the wire harness back to the connector under driver's side dash. Found the harness caught between the connector bracket support bolt and firewall. Looks like it may have been shorting out there. Bracket was pretty sharp. All's well now. A/C working fine. I'll check the wires out in a.m. for any damage or cuts.
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Old 03-12-2010, 02:13 AM   #16
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What are you going to do with your old panel? Might be interested in buying it..
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Old 03-12-2010, 02:30 AM   #17
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Haha, since you fixed yours, wanna fly out and come fix mine? Mines only working on high and only when it feels like it. Glad to hear you fixed your problem though.

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