the connector with one brown and one black wire is the Auxiliary Battery Relay Electrical Connector. If you don't have dual batteries, its has nothing to plug into.

 

I decided to change the low pressure cycling switch. At the parts counter, the parts guy noted that there was an attached tsb for this part. bulletin 03-01-39-007 addresses intermittent a/c operation, with the low pressure cycling switch being a possible fault. Even though the tsb is for model years 2002 to 2003, I bought and installed the updated switch which was listed for my 2000.


The updated gm part # is 89040362; my cost was $37. Its a simple screw in installation as the accumulator fitting has a Schrader valve; so the system does not need to be evacuated.


I will post back if it fixes it.

 

yep, its fixed.

 

I recently had an a/c in my 1996 c2500 that didn't work. The air blew but the compressor would not cycle on.

Anyone experiencing air blowing but not cold should first check to see if your compressor kicks on when you turn on the a/c. Find out where it is and check it, then troubleshoot from there.

In my case the compressor wasn't turning. If your compressor isn't engaging don't try to put freon / r134a in it. The gauge won't read right and the compressor simply won't take it.

Next I check all a/c related fuses, which were fine, so I moved on..

Then I pulled the a/c relay and replaced it with my horn relay and vice versa, since these 2 relays in MY truck are the same. The horn still blared and compressor still didn't turn on. This is just to test the a/c relay. You can also test the relay by putting power on it from the battery with wires and seeing if it clicks on (look this up on youtube, it's easy).

Since, mine was easy to test with the horn I moved on. I ran a wire from the hot battery terminal to the a/c relay node (while the relay was unplugged ofcourse) and this finally kicked my compressor on. ( you can research how to do this also on youtube, search for bypassing a/c relay, or hotwiring the relay, etc). Since my compressor was finally on, I plugged in the can of r134a and recharged the system. The compressor sucked it up and started blowing ice cold in the cab.

When I was happy with the level of r134a in the system I removed the hotwire and plugged the a/c relay back in. With a freshly charged freon system the compressor still did not engage on its own.

Next, I focussed on the low pressure switch on the accumulator. I found out that you can hotwire / bypass this switch as well. Unplug the 2 wire connector from the accumulator and use a paper clip, wire, or even a staple to bridge the 2 connectors in the wire (not the accumulator connector). When I did this my compressor engaged, so I figured that my switch was bad.

On my truck the switch screws on / off easily with pliers, and with a replacement switch (got from salvage yard), I replaced it and now my a/c works all on its own. Fixed!

If you are having issues with a/c and want to troubleshoot on your own I would research each one of these steps for YOUR model / year and proceed with caution. Hope this helps!

 

The mystery plug I believe your referring to is for vehicles with rear system