A/C problem, almost at wits end

[sbduncan]

I am having a problem with my A/C and I would like some help, maybe I am overlooking something. Truck is a 1996 GMC C1500 with 5.7l.

The high side service port blew out, so I replaced it and vacuumed/recharged the system. After a couple of days the compressor started short cycling, but after about 10 minutes of driving it would stay on. After a couple more days it wouldn't kick on at all. I hooked up my gauges and I still had a charge. The compressor wouldn't kick on by jumping the low pressure switch on the accumulator.

I used this very nice write up and thought I had it narrowed down to the control unit. I ordered another control unit off eBay and system behaves the same. I've checked the A/C fuses and jumpered both pressure switches. The only way I can get the compressor to kick on is by jumping 12v to pin 30 in the relay socket.

Is there anything I may be overlooking? Thanks in advance, I am tired of this Alabama summer.

 

[Dubs]

Did you try replacing the relay? If you jump it and system works, I'd try that.

 

[Oldblue98]

Low side switch possibly bad !? What does the gauges say when you jump it and run it ? Is it over charged / under charged ? When it is running is it cold/hot/cool ? Have you felt the line going into and out of drier/accum to see if you have a blockage ? Just ideas for you.

 

[sbduncan]

Thanks for the suggestions Dubs and Oldblue98, I appreciate y'all taking the time to read and reply.

I did some more checking last night, and found a blown 10 amp A/C fuse in the underhood fusebox. This fuse supplies power to the A/C relay. When i went to switch the A/C on, I heard a pop
from the new-to-me control panel. I had a chance to look at it today and found a blown transistor on the board. From what I have read this is one of the most common failure points with these control units. The post I linked above suggested soldering a jumper across the two pins I marked, and this solved my problem. I hope this helps someone out in the future.

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[Dubs]

Glad you got it fixed, or at least found the underlying problem.