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Blowing compressor fuses

Malc on Sat March 29, 2008 7:26 PM User is offline

Year: 1989
Make: Cadillac
Model: Eldorado
Engine Size: 4.5L
Refrigerant Type: R-12

Car is blowing the 15 amp compressor fuse under the hood. This fuse is located next to the 20/30 amp A/C relay. Probing with a multimeter I have noticed that neither of the two legs of the fuse are grounded as are the other fuses in this box. Also, when I start the car and turn on the A/C the fuse will show a draw of 30 amps when the compressor engages, it runs awhile, disengages, and when it reengages it spikes again to 30amps and blows the fuse. My knowledge in this area of trouble shooting is very limited. Any help on which way to turn will be appreciated.
The compressor assembly is relatively new with less than 50 hours on it.

mk378 on Sat March 29, 2008 10:38 PM User is offline

Check the resistance of the compressor clutch coil. It should be 3 to 4 ohms (be sure your meter reads zero ohms with the probes touched together). If it is much less than that, the coil is faulty. Also if it's the type of coil with 2 terminals, there should be no contnuity from either terminal to ground with the harness unplugged. If all that is OK, there is something else in the circuit drawing too much current.

Malc on Sun March 30, 2008 2:51 PM User is offline

The reading across the two prongs of the coil on the compressor reads 0.0
Checking the individual prongs to ground, they both read open. Not grounded.
I have a feeling this is not good.......
Any input is welcome!

Edited: Sun March 30, 2008 at 3:03 PM by Malc

mk378 on Sun March 30, 2008 6:46 PM User is offline

Do you have a warranty on that compressor?

On most cars, the coil can be changed without removing the compressor or opening the refrigerant system. Some special tools will be necessary.

As a final check you might put a 15A fuse in, but leave compressor unplugged, start the engine and turn A/C on and make sure the fuse holds.

Malc on Sun March 30, 2008 10:15 PM User is offline

I tried running the A/C without the compressor lead plugged in. After several minutes, the fuse was still good. Unfortunately the warranty has expired as this is my "Sunday Cruiser" low mileage on the compressor but a couple years old. Since I don't have the special tools the manual calls for to replace the coil............ I guess it's time to bite the bullet and replace the compressor. Thank you for your help.

mk378 on Sun March 30, 2008 10:32 PM User is offline

The tools are not expensive, especially compared to having to buy another compressor and deal with the R12. Be sure to get the ones that actually fit your compressor though as GM used two different standards for the shaft threads. You should be able to pull a good coil off of a junkyard compressor since most have trouble with something other than the coil.

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