Ok I'm not getting power at the high pressure switch by the blower motor so the a/c is not working but if the switch on the compressor is given 12 v the a/c works, any ideas. 92 lt1

 

It could be low pressuer in you'r system try to short the swicth out and see if the compressor kicks on.

You could have a leak somewhere.

I just rebuilt my complete system and converted it to 134 it cost like $300.00 for all the parts including all new O-rings and $70.00 to get vacuumed and charged.

 

PM Suncr. He seems to be the resident C4 AC expert. GC

 

It has a full charge and no, shorting the switch wont turn it on but as I said when I put 12v to the switch on top of the compressor it works

 

Dont mean to hijack your thread, but I am having similar issues.
The connector on top of the compressor has 2 wires. Black and Green. When I turn the AC on, the compressor wont run, but I have 12.6 volts on the Black wire and 0 volts on the Green wire. Is this correct.

Where do I find the pressure switch to try shorting to see if that turns on the Compressor.

8Valva

 

Believe it's on the hp line next to the blower fan, goes right down the side of it. When I short mine I get nothing so I have no power from the head unit to the switch.

 

You need to put power to the green wire that should run your compressor.

 

Is it normal to have 12 volts also on the Black Line ?

8Valve

 

Any of you master minds have any ideas?

 

There are variations by Year.

For '92, compressor is controlled by the PCM. It receives an a/c request via the Controls (Manual Air) or Programmer (Electronic Air - which got a digital signal from the Controls) and when it does, it drives (grounds) the compressor relay. A nano second before it drives the compressor, it checks to see if there's any gas in it - that comes from a Pressure Sensor on the High Side or smaller line from the Condensor to the Evaporator. A full system should have about 80 psi when it's sitting still and if it's got it, the PCM grounds the Relay. On the ground side of the Relay is the Low Pressure Switch - Big tube, top of the Evaporator on the Firewall and the Switch the OP seems to be referring to. That Switch needs 50 psi of static pressure to close the circuit. It's used to keep the Evaporator from icing over and to shut the system down when there isn't enough gas to move the oil that lubes the compressor. Realistically, if it doesn't have at least 50 psi when it's sittlng still - there's no gas in it so you need to have it leaked checked and then recharged.

Bottom line - sounds like yours is out of juice. Go to an a/c shop and have them check it out AND/OR scan it to see the Pressure Sensor Signal AND/OR hook up a manifold gage set so you can get your static pressures. Once you've got that info you'll know what to do next.

 

Ok, I have a full charge and when I short the hps I get nothing but if I give power to the switch on the compressor the system runs and cools, so basically I seem to have no power to the hps.

 

on my 90 the green wire out of the ECM went to the Switch, it was cut.

 

Disconnect and reconnect the battery to clear any glitches.
If that doesn't work, the Relay may be dead or there's a bad connection at the Low Pressure Switch. Take your DVM and make sure the contacts are closed. If they aren't and you've verified static pressure of 50 + psi, you need a new one. If the contacts are closed, try disconnecting and reconnecting the harness - hold it onto the switch - wriggle it around. If you need to replace it, it's on a Shrader, so you don't need to discharge the system. Otherwise, scanning it to verify the a/c request and pressure sensor signal would help. There's also a possibility that's it's plugged up, but that would be a major logjam if it's pushing 400 plus psi when it's off - knowing you static & operatings pressures - along with the outside air temp - would be helpful.

 

My son's 96 LT1 is having a similar problem right now. Compressor clutch only engages when he jumps 12V to the green wire on the compressor, then A/C blows cold.

He bought a CHINA low pressure switch and new plug in, but a/c still doesn't blow unless the green wire is jumped.

DOES ANYONE HAVE THE ACDELCO PART NUMBER FOR THE 96 LT1?

I want to send it to him: I'm in TX and he's in D.C. and we're trying to solve this over the phone.

Any problem with just leaving the green wire jumpered to 12V until we come up with a fix? There's a heat wave on the East coast and he's suffering.

Thanks,

Jake

 

Note that there are two switches in the system, both must function for the clutch to engage, the wiring diagram in the FSM is the best way to troubleshoot the system.
For switch ID and part numbers for cars between 92 and 96 see post #2 in this link.
http://forums.corvetteforum.com/c4-t...re-switch.html

 

so my 92 wont kick on either. when i first got the car in feb. this year, i noticed every time id start it up, the compressor would kick on. being winter time, and the fact the climate control was OFF, i figured id simjply unplug the wire clip. summer time comes around, and i plug it back in, the clutch wont engage. i figured it was low/empty, so i went to the parts store, bought a few cans of 134a freon, and tried to fill it. wouldnt kick on then either. so, i manually started it with the green wire to the battery, sucked the freon right on in there. i used the rest of the stuff on my truck, figured after the one can was in, id leave it alone til i got more cans of freon. so, now at work, (auto shop) i hook up gauges, vacuum the system out, and it held a vacuum. so i go to fill it, static pressure was at about 80 or so before i jump started the compressor again. blew cold, charged it up to about 40psi while engaged, took the jumper off. static is now about 115, and its probably 85~ degrees in the shop. before a few days ago, my second cooling fan wouldnt come on either, so i ran a jumper from the regular fan relay to the secondary. (would run too hot in city traffic at 110 degrees outside & no front air dam) so now, i make shift fitted an air dam on it, runs about 10 degrees cooler normal driving, and about 20 degrees cooler sitting in rush hour trafic, with the both fans running. i unplugged the battery, let it sit for a minute, hooked it back up, and no change. was going on the suggetion of killing power in hopes to get rid of and computer glitches. unplugged it again, let it sit for about an hour. jumper wire removed from the 2 relays. at start up, one of the cooling fans comes on, no compressor. shop temp according to the car is 92 degrees, static pressure about 110. read all the comments here, but not sure what to do next? my boss let his alldata subscription lapse for some reason, otherwise id go about it through their diagnostic methods. i dont have any service manuals for this thing. any methods or suggestions to determine where my problem lies? thanks in advance, hope this is still a llive thread.

 

Assume it was converted to R134 before you dumped in a can or two?

Sounds like a bad relay to me. That controls the ground side of the Compressor Clutch and if it was running with the Panel off, the contacts may have been stuck. You disconnected it and couple of bumps later, they opened and will no longer shut. So I'd replace that (and check wiring to and from the Relay while you're at it), clear memory, and see what happens. Then if it still doesn't work, hookup the shop's scanner and see if there's an a/c request when you put it on Auto (which is what the Alldata site will tell you to do).

 

PS - do make sure the Low Pressure Switch contacts are closed and try wriggling around the Connector or holding it onto the switch - that's usually a problem with the '94 and up GM's, but it's worth a try.