I have a 03 Suburban the AC Compressor clutch burned up. I just bought a new compressor dryer etc and put it all on. When I went to charge it up I noticed the Compressor would not engage even with the low-pressure switch jumped. So I checked the fuse it was blown. Replaced it and it blew instantly. Pulled the relay and tested it on my other suburban and it worked so the relay is good. I used a jumper for #37 and #87 and smoke instantly from the jumper.

At this point, I am sure it's just the dark green wire from the relay to the compressor that has the problem, Before I replace that (the plan is to remove the fuse box under the hood and cut the dark green wire about 2" from the box and attach a new wire and run it to the compressor clutch) Just trying to make sure there is nothing I may have overlooked before I go to replacing the wire. I did use a power probe direct on the compressor and the clutch does engage and disengage. I tested the relay there is constant power #30 and #86

Also, #87 if I put a volt meter for continuity and use battery neg and probe #87 there is continuity, and the speaker in the voltmeter sounds. This is why I believe the wire going from #87 to the compressor has a short in it somewhere.

Thanks in advance for the input.

 

Could be some rodents were chewing on the wires, causing a short? It's very common. Could be you have a defective compressor? Should have come with 4 oz of PAG oil, but I've heard that some are sold dry. If that was the case, and you replaced the receiver/dryer, you need 8 oz of the proper PAG oil for your A/C system. I'd replace the orifice tube as well on a vehicle that old. It needs it after all this amount of time, if you did not do that already.

 

I replaces the orifice tube as well. I also bought 2 big cans of flush and blasted the lines with it sprayed in one until it came out the other. Then blew them out with my air compressor. Installed all the new parts I did add 7 OZ of oil. hooked up all the lines hooked up my vacuum pump applied max vacuum let it sit for +- 5 hours it held. That's when I fired up the engine jumper and wired the cycle plug that's when I noticed the compressor was not kicking on and found the bad fuse.

Replaced it and it blew instantly. At that point, I used my power probe and went straight to the compressor unplugged it used my power probe and the clutch engaged and disengaged fine. Now the Relay has #30 #85 # 86 #87 #30 should be constant 12v which it is #85 is Ground #86 should be a signal from the dash button #87 is 12v to compressor. On broken suburban (I have 2 a 03 and 04) #30 has 12v #85 ground works #86 has constant 12 v does not go off when the button is pushed (my good suburban #86 goes to 2.5V with button off 12V button on) #87 has no voltage ever (My good suburban has 12v when ac is on compressor engaged)

If I put 12v direct to #87 on broken suburban smoke and fuse blows
I put the relay from the broken Suburban in the good suburban and AC works fine so Relay is good.

Just hate hacking on wires of a factory harness so trying to avoid doing that.
If nothing I missed test wise I guess the next step is to cut ac wire on back of the hood fuse box and run a new wire to the compressor.
I am just stumped on the #86 having constant 12v on the broken burban and on the working one it changes to 2.5 when ac button is switched off. thinking maybe the control unit however stuck on sending 12v so the compressor should come on just not turn off. I hate electrical issues.

 

I just ran a new wire from the relay to the compressor and have the same issue. Upon re-testing the relay terminals post with it plugged in I realized the #85 ground actually has 12v on it for some reason. I know ECM is supposed to ground the relay.
To recap Relay #30 12V #85 12V #86 12v (no matter if ac is on or off ) #87 never gets any voltage My power probe has a relay testing pigtail I hooked that to the relay and it is 100% for sure good.

The system is empty (less the 7oz of oil and 1 12oz can 134 I got to go in) Normally putting on a jumper in the cycle switch to kick on an ac compressor for charging. What I have always done anyhow. With Jumper in ECM still not grounding. Guess either the high-pressure switch is bad or bad ECM or a dirty ECM connection. The suburban runs perfectly no check engine lights nothing so I find it hard to believe it could be a bad ECM.

 

I don't. ECM's are not infallible. I am an older man and cannot believe all the faith that people put in onboard computers, when they didn't even exist 30 years ago. They control almost everything in a modern vehicle, including the air conditioning system.

I come from an age when computers were massive, and most cars still used cables and wires (not connected to a computer) to control their vehicles systems. A/C in a car was a luxury, not standard equipment. I was in the works to become an auto A/C tech, and even then there were no computer-controlled systems. Cars had an electronic ignition control unit to replace the points/condenser system in the early 1970's.

That doesn't mean I don't know about computers. I very much do and a bad ECM is a possibility. Many A/C systems no longer use a high pressure switch, just low pressure, likely to save production money. I would suggest that you have your OBD II system scanned by a professional technician.

 

Just updating for if anyone else ever has the issue. It was a bad AC compressor. The clutch was "engaging" however it was tasking a ton of current to get it to pop out. Thus why it was popping the fuse. Swapped it out for another one at the parts store and was instantly back in business. Put vacuum on it for 4 hrs it held pressure and when I charged it up it filled right up. Thanks for the input.