A/C issue on a '92 Silverado

jtdt175 · 03-30-2009, 01:45 PM

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.

ukrkoz · 03-30-2009, 05:16 PM

OK, so let's sum up:
1. your a/c clutch will not engage
2. you could jump clutch off battery (done that myself) and clutch will engage
3. when clutch was jumped, freon was sucked into the system and after that it all works fine?
4. you tried to jump the pressure switch, and it gives no results? (basically, you do not jump pressure switch. you shorten both contacts in it with aluminum foil or copper wire)

first things that come to mind: fuse? fusible link (you are blessed, as in any domestic, with multitude of those)? SWITCH in the dashboard? climate control unit as a whole? fan was not turned on whilst trying engage a/c?

you need to get yourself voltmeter and work it all up from the clutch plug. does it have power on the clutch plug with a/c switch AND fan switch on?
is pressure switch sending any signal out?

Shortbus · 03-30-2009, 09:00 PM

I had a 92 1500 and had the same problem. I ended up replacing the dash control panel and it fixed the problem. At the time I happened to work the parts dept of a chevy dealer so I grabbed the control panel off the shelf and plugged it in to my truck to verify.

I think in 93 GM updated the control panel due to some failures so they had a slightly different appearance than the original that came with the truck new.

Also moving this post to the C/K forums.

jtdt175 · 03-30-2009, 09:21 PM

ukrkoz, when the clutch was jumped with a direct line from the battery everything worked until I took the wire off the terminal on the compressor. Also I put a clip in the cycling switch to jump it which was metal and a good conductor.

3. when clutch was jumped, freon was sucked into the system and after that it all works fine? 4. you tried to jump the pressure switch, and it gives no results? (basically, you do not jump pressure switch. you shorten both contacts in it with aluminum foil or copper wire)

This idea of the control unit in the dash we will call the user interface of or temperature control. I wouldn't think it has a fuse in the back of it like a aftermarket stereo has or would it.

Shortbus, I was thinking if the control panel could be the issue but I had not but a gut feeling, would you recomend to find one from a 93 and slightly newer or stick with another '92? are there any differences in the 93's it should still bolt in and still plug in and control the hvac right? Thanks guys, I appriciate the input.

Shortbus · 03-30-2009, 09:45 PM

Honestly I can't remember. I recall the 89 thru 91 had different looking buttons and the 92 up were redesigned.

I would stick with the 92 I think it was just the AC blue button that changed.

Do you have any friends that have a truck like yours that you could do a little experimenting with? The controls are fairly expensive or at least they were. I hate to see you shell out money for one and that doens't fix the problem.

Maybe you could get one from a salvage yard. Don't go to ebay even though I see a lot of them on there, you never know what your getting. Best thing is to find a temporary donor and put it in your truck and see if it solves your problem.

brcidd · 03-31-2009, 07:22 AM

Guys--- you are forgetting the obvious.....

The flashing a/c lite for 2 minutes means a code is set in the control head- unhook the battery for 10 seconds will reset the code----that is why replacing the control head works-- it powers down when you replace it...

'there is a TSB on this exact condition--'91 and '92 C/K trucks experienced this...

jtdt175 · 04-03-2009, 06:43 PM

Ok today I disconnected the battery waited a few minutes and re-hooked it up. The AC blinking light went away and the compressor clutch kicked in and I was able to charge the system. Everything works great. Thanks guys.

Shortbus · 04-03-2009, 09:53 PM

Quote:

Originally Posted by brcidd

Guys--- you are forgetting the obvious.....

The flashing a/c lite for 2 minutes means a code is set in the control head- unhook the battery for 10 seconds will reset the code----that is why replacing the control head works-- it powers down when you replace it...

'there is a TSB on this exact condition--'91 and '92 C/K trucks experienced this...

Thanks great info

heellbilly · 07-08-2009, 09:43 PM

I would just like to say thanks about the tip on jumping the compressor. I just went out and jump mine and it engaged. It started working. I was able to put in about 3/4 of a bottle of R134a. I will need to purchase more tomorrow and fill it the rest of the way. We will see how long this old thing last. I have a 91 Sierra 4X4. As soon as I can get the cab corners repaired she'll be in great shape. Having no AC in Georgia really blows during the summer. Once again thanks a million!!!!!!!!!

wildturkey_666 · 07-07-2014, 02:17 AM

Mitchel on demand says remove ac controller and remove dark green wire #59 from connector fold it back and tape it

broughy84 · 09-01-2014, 05:17 PM

This is exactly what I did to mine with the same problem. Cut the dark green wire, tape it over. It's some sort of a power surge sensor or some baloney. Mine went whako when I mounted my strobes in the truck as soon as they were turned on, boom no ac.

wildturkey_666 · 09-02-2014, 10:48 AM

if ac is blinking when ya start up disconnect bat fer a few min that should reset the ac controller there is a recall for this basicly remove ac controller unplug connector remove dark green wire tape it up reinstall should work I havent hade an issue since I done that im still rollin r12 original charge lol

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