1999 GT PCM or CCRM, AC Problem - Ford Mustang Forums : Corral.net Mustang Forum
 
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post #1 of 17 Old 07-30-2008, 10:50 PM Thread Starter
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1999 GT PCM or CCRM, AC Problem

I have 1999 GT, my AC is not working, tried to bypass high and low pressure switch's still no power to the ac clutch. Hot wired ac clutch and ac works great, but I know can't run it like that, but at least I know ac clutch is good.

I tried the test for the ccrm.

Pin 23, that is for the ac clutch. I tested it and has 12v, this should indicate the ccrm is okay. Test pin 21 and there is no power. I was told that it has to have 12v. Pin 21 supply's the 12v for pin 23, I do not how I could have 12v to pin 23 if there is no power at pin 21. I also checked pin 22, but there is no power either. That indicates a the pcm has grounded the relay for the ac clutch.

I have check the fuse and wiring looks good. I have also read there is an open circuit 198, DG/O which cause no power to pin 21. I have no idea where this circuit is.

So my questions is could the pcm be bad or is the ccrm bad.


Last edited by Keno; 07-30-2008 at 10:57 PM.
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post #2 of 17 Old 07-30-2008, 10:57 PM
 
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What year car and what engine?

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post #3 of 17 Old 07-30-2008, 10:59 PM Thread Starter
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Sorry about that, 99 GT 4.6.
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post #4 of 17 Old 07-31-2008, 12:19 AM
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have you tried undoing the battery and then connecting it back and turning your key to the on position with everything off inside the car? its a shot which i found out on a 99 gmc jimmy...have to reprogram the truck to get a/c to work. who would have guessed!?!?!
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post #5 of 17 Old 07-31-2008, 08:59 AM Thread Starter
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Sure did, I'm at a lose. I guess I will just start replacing parts. I thought if the pcm was bad there might be some codes, but none.
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post #6 of 17 Old 07-31-2008, 05:55 PM
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pin 21 is circuit 198. It comes from fuse box thru connector. Check the fuses, then power on connector, pin 4.
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post #7 of 17 Old 07-31-2008, 07:16 PM Thread Starter
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The fuse is ok, I will check the power on pin 4. where does pin 4 go to.

I figured out how to get the ac working until I can figure out what the problem is. I tapped into the wire coming out of the low side pressure switch, the green with a yellow stripe. I ran a wire to to the 12v side of ac clutch, black with a yellow stripe. I had to cut the wire because just splicing into will not work. I just took a 70 mile trip and everything is working fine. AC cycles properly and ac is cold. The only thing I do not have is the ac shutting off at full throttle.

I think its a PCM problem. I have had issues with the ac not working while driving on the highway. I would turn the ac on, but it would not work. I would come to a stop and pay a toll and the ac would come on and I would not have any problems for weeks. Then it would happen again. I would slow down and the ac would work again.
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post #8 of 17 Old 07-31-2008, 10:47 PM
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Quote:
Originally Posted by Keno View Post
I have 1999 GT, my AC is not working, tried to bypass high and low pressure switch's still no power to the ac clutch. Hot wired ac clutch and ac works great, but I know can't run it like that, but at least I know ac clutch is good.

I tried the test for the ccrm.

Pin 23, that is for the ac clutch. I tested it and has 12v, this should indicate the ccrm is okay. Test pin 21 and there is no power. I was told that it has to have 12v. Pin 21 supply's the 12v for pin 23, I do not how I could have 12v to pin 23 if there is no power at pin 21. I also checked pin 22, but there is no power either. That indicates a the pcm has grounded the relay for the ac clutch.

I have check the fuse and wiring looks good. I have also read there is an open circuit 198, DG/O which cause no power to pin 21. I have no idea where this circuit is.

So my questions is could the pcm be bad or is the ccrm bad.

Pin 21 DG/OG is hot at all times from fuse 24(20 amp) in the battery junction box,this is the switch side of the relay, pin 12 RD is hot in the run postion and is supplied power from fuse 2 (20amp) in the under dash fuse panel, this is the coil side of the relay. Pin 22 PK/YE is the ground side of the coil and is grounded by the PCM on pin 69. Pin 23 BK/YE supplies power to the clutch. Now how this works is power is supplied to coil pin 12, when it is grounded by the PCM on pin 22 this creates a magnetic field which in turn closes the switch so power flows from pin 21 to pin 23 .
Does this help?
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post #9 of 17 Old 08-01-2008, 12:41 AM
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chuck943 nailed it.
I can e-mail you diagram.
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post #10 of 17 Old 08-01-2008, 09:19 AM Thread Starter
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Kind of, but it does not explain why I have power at pin 23 and no power at pin 21. If pin 21 supplies the power to pin 23 there should be no power at pin 23. And if there is power at pin 23 the ac clutch should work. The only thing that can explain this is I have the wrong diagram for the pins on my ccrm.

rasputinlv, I diagram would be great. I will have to send it as a pm, it will not let me post my email.

Thanks again for everyones help.

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post #11 of 17 Old 08-01-2008, 10:47 PM Thread Starter
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rasputinlv,

Thanks for the wiring diagram. It seems the one I had was wrong. There is no power coming from the black and yellow wire. Thats pin 23, so this tells me the ccrm is bad. To be more precise, the relay in the ccrm for the ac clutch is bad.

Thanks for your help, without this forum, it would have been hard to get the right diagnoses.
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post #12 of 17 Old 08-01-2008, 11:05 PM
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Quote:
Originally Posted by Keno View Post
rasputinlv,

Thanks for the wiring diagram. It seems the one I had was wrong. There is no power coming from the black and yellow wire. Thats pin 23, so this tells me the ccrm is bad. To be more precise, the relay in the ccrm for the ac clutch is bad.

Thanks for your help, without this forum, it would have been hard to get the right diagnoses.
Are u sure that the relay is being energized? Make sure the pcm is grounding the coil side before just replacing the CCRM.
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post #13 of 17 Old 08-01-2008, 11:26 PM Thread Starter
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Will do, thanks again.
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post #14 of 17 Old 08-01-2008, 11:29 PM
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Yeah just take a jumper wire and ground pin 22 the pk/ye wire and see if it energizes and powers up the compressor,if it does then the CCRM is ok and u will need to look at inputs to PCM.
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post #15 of 17 Old 07-25-2016, 12:27 AM
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2000 Mustang GT

My 2000 GT we changed the switches and the CCRM and checked every wire. The mechanic called Ford and the Technician told me that its more and likely the PCM... I have new compressor installed thought it was it but nope.... I live in Arizona and its freaking hot man! Does the PCM have anything to do with the AC compressor? We bypassed everything and it kicked on the compressor
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post #16 of 17 Old 07-30-2016, 08:12 AM
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You can replace the relay itself fire a few dollars. Don't remember the part number, but radio shack sells it. There 5(I think) pins you have to desolder, pull the old relay out, put the new one on and resolder.
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post #17 of 17 Old 07-30-2016, 10:35 AM
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Quote:
Originally Posted by Dylan09 View Post
My 2000 GT we changed the switches and the CCRM and checked every wire. The mechanic called Ford and the Technician told me that its more and likely the PCM... I have new compressor installed thought it was it but nope.... I live in Arizona and its freaking hot man! Does the PCM have anything to do with the AC compressor? We bypassed everything and it kicked on the compressor

absolutely the PCM something to do with the compressor.

If you look at good wiring diagram for your year, you will see which pin to test.

Starts, compressor is delayed

WOT, compressor turned off, and delayed to turn back on.

ECT, if overheat,,,,,the compressor is turned off, and delayed turned on.

ECM, needs to have control, and needs to know the request.

You supply the diagram, I will tell you what to look for.

89 GT gr-40, KB2200(10psi), tweecer R/T,LC-1, 22gal cell, w/tailpipes.
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