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Discussion Starter #1
this is my second ccrm that i popped!!!!!
and its always the a/c clutch relay.
i have a new clutch on the compressor and it still blew the relay.
this is the process that i did to get to the point that i am now:
1 replaced CCRM
2 replaced a/c clutch ( brand new )
3 shimmed the clutch to .018th of an inch
4 turned car on, let it idle for a min, then jumped the low pressure switch
5 turned the A/C on
6 clutch is TRYING to cycle, but car is surging up and down
7 shut car off reshimed to .012 ( almost to close but doesn't grind )
8 repeated step 4
9 clutch did not cycle.
10 used snap-on test lamp to see if there is voltage to clutch and there is, but still no cycle
11 shut car off
12 turn car back on car is surging up and down..... relay is blown

what is going on????
 

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Couple thoughts

-Can you verify it is blowing the CCRM? If this is the case, the diode that is parallel with the AC clutch is blown. When the AC clutch is shut of the magnetic field from the clutch coil collapses producing a voltage spike(inductive kick). They use a diode in parallel with the coil to drain this voltage spike. If the diode is open, the couple thousand volts will definitely fry some electronics. Same concept as the ignition coil.

-If the CCRM may or may not be bad, check that the IAC(Idle Air Control) valve isn't sticking. The CCRM will drop the AC clutch if RPM falls too low. If the IAC is sticking shut, the AC compressor can pull RPM below that point and cause it to drop.

Hope this helps and keep us posted.

Mike
 

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Discussion Starter #3
Couple thoughts

-Can you verify it is blowing the CCRM? If this is the case, the diode that is parallel with the AC clutch is blown.
Mike
where would this diode be in conjuction with the ccrm and the A/C clutch?
 

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Very nice post by Mike. Mike can correct me, but I'd guess the diode should be pretty close to the compressor itself. IIRC on Aero Mustangs you can just trace the clutch harness upstream a little and you hit the diode. I bet most models of a similar generation/design are similar.

The WOT relay (in the CCRM) might actually be a solid state unit. It is on 94-95 Stangs for instance.
 

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The two schematics I have are for a 96, and show the diode inside the CCRM... I thought it was external. How did the IAC look?

Mike
 

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Discussion Starter #6
brand new IAC ... but i have been reading up on some things about my problem. if i do have a bad compressor and the clutch is trying to turn over the compressor, in thus causing it to pull more power from the ccrm and blow the relay is that possible???
 

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Yes, the schematic shows a solid state relay. So overcurrent could possibly blow it. I would think it would take out the fuse first though. Is your compressor easy to turn by hand? Also, it's a long shot, but check the ground from the CCRM module pin15-black wire. If the gound was poor or intermittent it could cause some issues.

Mike
 

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I have a ccrm from my 96 v6. If you want it you can have it for 10+ shipping.

Zero
 
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