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P0645 Question

 
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  #1 (permalink)  
Old 23 Aug 2011, 11:58 pm
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Default P0645 Question

I had my wife's PT in the shop today changing A/C fan. Once the fan was fixed, the A/C was blowing cold. 15 minutes later it started blowing hot air again. Gee $300 for nothing I did the key trick and code P0645 came up - A/C Clutch Relay Control Circuit. Has anyone changed it? Is it expensive and where is it located?
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Old 24 Aug 2011, 05:02 am
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Default Re: P0645 Question

According to the diagram below, it's inside the PCM (Powertrain Control Module)

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Old 24 Aug 2011, 10:57 am
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Default Re: P0645 Question

Thanks for the diagram. A few more questions. Is PCM a black fuse box located behind air box? Just came back from the shop and the technician said that the compressor needs to be replaced. He switched relays in that fuse box and the compressor still didn't kick in. Is it possible that code P0645 would show if the compressor is dead? I just can't justify spending so much cash again if it's just a relay that he didn't find.
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Old 24 Aug 2011, 01:37 pm
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Default Re: P0645 Question

The PCM is the silver box hanging on the firewall. Can't really answer the other questions.
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Old 24 Aug 2011, 03:10 pm
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Default Re: P0645 Question

The A/C clutch relay is in the PDC (the black fuse box behind the filter box). There are many other relays just like that you can swap it with. I would suggest you swap it with the horn relay. When you turn on the A/C does the compressor clutch engage? Did you check both fuses?
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Old 24 Aug 2011, 05:51 pm
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Default Re: P0645 Question

Thanks for confirming the location. I did swap fuses but the compressor still wouldn't engage. The mechanic said there wasn't "+" nor "-" at the compressor.

Last edited by the_jeep_now; 24 Aug 2011 at 10:21 pm.
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Old 24 Aug 2011, 09:46 pm
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Default Re: P0645 Question

According the wiring diagram, one side of the clutch coil should always be grounded. The other side is 12V switched by the A/C clutch relay. To track down this problem the following needs to be verified:

1. Pin 2 of the A/C clutch connector is grounded.
2. Pin D5 of clutch relay is 12V at all times.
3. Pin D4 of the clutch relay is 12V with the ignition key in the on position.
4. Pin D2 has about 12V on it with the iginition key in the on position and A/C off.
5. Pin D2 has about 0V on it with the iginition key in the on position and A/C on.

If you can't verify these, you need to find the source of problem.
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Old 01 Feb 2014, 01:41 am
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Default Re: P0645 Question

If someone now the answer to this problem please answer back, i have the same problem when i check the relay doesnt get "-" power for some reason, i believe but not sure that could be the a/c on switch, can someone help please!!!
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