custom_car_man87

Hello everyone, I decided to make the switch to GM after owning 3 Fords. I purchased a 1999 new body style 1500, 5.3 engine, 164,000 miles. Engine runs great and transmission doesnt skip a beat. The truck does need some minor cosmetic repairs, but what truck doesnt!

Anyways, I am having a problem figuring out my AC in this truck, and as I live in Texas, I need that AC!

First off, the clutch will not engage. I have done some testing. I have power all the way down to the clutch coil. I have alos checked the ground circuit and all is well there. Now when I command the AC to turn on, the 10 amp AC fuse blows immediately. The clutch will turn freely by hand. There is also a leak in the system, which is why I had to supply direct power to the clutch to determine it wasnt kicking in. Now today I charged the system, just to see if the low pressure switch would actually command the AC to turn on, which it seems to have done so since the fuse blew immediately only when commanded. If i dont turn the AC on via the the dash controlls, the fuse wont blow. If the AC is discharged all the way to 0 psi, and I try to turn the AC on, the fuse WILL NOT BLOW, since the low pressure switch is not commanding the system on.

I checked the resistance at the clutch field coil and im getting between .01 and .02 ohms of resistance. I read somewhere that it should be between 2-5 ohms.

Im assuming the clutch it shorted, which is why its blowing the fuse, only when commanded on. There is quite a bit of rust on the front of the compressor hub, so I guess im putting 2 and 2 together.

Can someone with electrical or AC knowledge confirm my assumption, or offer any other advice? Ive heard that its very rare for the actualy field coil to go bad, but since this is my first GM, im hoping thats all it is.

Thanks for any help anybody can offer.

kevinkpk

Your assumption is also mine. Unplug the connector to the clutch, turn on a/c doses it NOT blow the fuse?

custom_car_man87

I have not tested the exact method you just described, but with the coil connector unplugged, I have supplied voltage to the wire, by jumping across the relay terminals, and checking for power down at the connector, which I did have power, and the fuse obviously did not blow, since there was power. I will try your exact method tomorrow.

cleveland63b

sounds like you're on track to me

custom_car_man87

Thanks a bunch guys, all other info or suggestions are welcome. I will try these methods tomorrow and report back tomorrow

custom_car_man87

Ok, here is what I did today. I had about 80 lbs of refridgerent pressure in the system. I put the AC fuse in, UNPLUGGED the wire from the compressor, and turned on the truck. I checked the power and voltage at the fuse, and was reading battery voltage. I went to the clutch wire which was unplugged and measured slightly under said voltage (less than half a volt difference, which is acceptable.) I then turned the AC switch on inside the cab to command the ac and and the fuse did not blow, whch confirms there are no shorts in the HVAC dash switches. I then shut the ac off, and shut the truck off. I put the fuse back in, and checked and all voltage was still there, and correct, at all locations.

Now I turned the truck back on, with the fuse in and the clutch plugged in, but the AC off, meaning the ac button was not lit on the dash, but the blower was on. Voltage was good at all places. I then pused the AC button, to command the clutch on, and after about a second, when the clutch should have came on, the fuse blew.

In my eyes, this is verifying that the clutch is indeed shorted, since I elemenated everything else. The fuse only blows when the clutch is plugged in, and the ac command is on.

What do you guys think now? Anything else I need to consider? Thanks again.

custom_car_man87

Well, anyone have any other advice to offer? I think im on the right thinking track with this one, but conformation is always good! Thanks

custom_car_man87

Anybody!?

kevinkpk

You answered your own question