A/c Issue On '92 Silverado

[jtdt175]

I purchased my ’92 Silverado in Dec. 2008. Since I got it the temperature control display has been blinking “A/C” for 2 minutes after starting, than goes away. From the owner’s manual and the GM service manual I realize this means there is a problem in the A/C system. I figured that it was low on refrigerant since the compressor clutch would never kick on, that and that is what it typically has been in the past with other older vehicles. After buying the retrofit 134a kit, I recovered the stuff that was in it, then proceeded to add the new stuff. The pressure kept rising but the clutch never engaged. I looked through the GM service manual and they suggested to do the obvious…Is there power to the wires i.e. the cycling switch and the clutch positive wire. There was not. I inserted a jumper on the cycling wires figuring this would complete the circuit telling me if the switch was bad or not. With jumping the cycling switch I still had nothing, the clutch never engaged. My next thought was well maybe the internal clutch relay or the pump was shot. So I ran a jumper from the positive post of the battery, to the positive post on the clutch relay itself. Then the clutch kicked in, I sucked in the 134a and everything was working. I also did this to the cycling switch, when I added power the clutch engaged and all worked. This tells me I have an electrical issue and the mechanical stuff should work. I don’t believe that it would be the cycling switch because with it jumped it should engage the clutch of the compressor and it did not, In fact it did nothing with a jumper on the cycling wires. I assume that I have an issue elsewhere that is causing a dead spot in the system or else the cycling switch would have power to it. Does anyone have any ideas or faced similar situation or hell even heard of any stories remotely similar to this? I would really appreciate any help, short of taking it to a mechanic who is going to charge me way more than the truck is worth to get this working again.

 

Thanks.

[Mike G]

First off, welcome aboard!

 

Secondly, I just asked my mechanic about the problems I was having with my 92. Se said that a lot of times on these older units, the compressor itself will develope a leak. His recommendation was a $400 repair to right all the wrongs. To me anymore, that's well worth a week of aggrivation on the driveway. Let me ask you this. Have you jumped across the "low pressure" switch on the accumulator (a little two wire lead/plug)? I had to do this to engage my system for charging, all worked fine until I lost pressure again...

--Mike

[jtdt175]

Thanks Mike G, I have jumped the switch on the accumulator, In the GM service manual they refer to that as a cycling switch. I did that with a metal clip, I know from building industrial HVAC's that is s bypass of the switch. I did get success when I added power to the dark green wire in the plug, I also had success when it was jumped with the clip and power was added, but jumped by itself I had nothing the clutch just did nothing. I would love to take it to a mechanic and say "here it's your problem fix it" but I was laid off in December and I am trying to finish school so it comes down to me doing all work, due to lack of cash. Good luck with your's.

[aljack]

What you need to do is disconnect the Battery for 10 seconds. This will reset the A/C control head. Its has locked out the A/C since the system was low on freon. Once you reconnect the battery, you can turn on the A/c by pushing the button and the compressor should engage, if you have a full charge of freon in the system, and the A/C lite should not blink.