Help with A/C problem

[HPG]

Tried the A/c for the first time, don’t work. I have 12 volts at the green and black wire at the connector going into the compressor. If I plug the connector back in, I hear a change in the engine, but the compressor won’t start. The inside fan is on and running. Is there a relay for the A/C ?. I used an ohm meter and the three switches on the A/C lines, one on the low and two one the high are closed. Could it be low on gas ? Or does it sound like the compressor. Thanks for any help.

[The Car Whisperer]

Check the charge level first, it could be low and this would keep the clutch from engaging.

[HPG]

OK,, I still have some R12. Would the switch on the low pressure side be open on a low charge.

[Moonunit 451]

What year is your car? I'm thinkin' if the charge was low the compressor would cycle constantly. I could be wrong. I just had to replace my compressor. If I let the A/C run for about a minute or two the clutch started to smoke, wouldn't turn at all.

If that's the problem, it was no fun to change in my car. You can replace the parts, but not without pulling the unit almost fully out of the vehicle anyway to get clearance for a wheel (pulley) puller. It's just as cheap to replace the whole unit anyway, probly around $200 for the compresor $130 wholesale if you got connections. It's not anything special, common on lots of GM stuff.

Remember, you need to recover your R-12 and it can be recycled. You also need to vaccum the system before recharging. If your short on R-12, I think it's a straight conversion to Freeze 12 which is a lot cheaper.

[jmccloud]

When there's 12v at the compressor connector, the 'other side' of the compressor should be at ground (electrically speaking) and the clutch should pull in and rotate the compressor. This is easy to see.
If not, either 1) the lead from the connector to the compressor clutch is bad, 2) the lead from the compressor clutch to ground is bad (both likely cheap to fix) or
3) the clutch is 'open circuit' and needs to be replaced 4) the compressor is frozen which would cause the belt to slip, smoke and screem (both a lot of work and several $100).
The control system won't supply 12v to the compressor connector if the charge is low or the temp is too cold.
What year do you have? I live about 30 miles up rt 1.
Hope this helps,
John

[Corvette-Pilot]

Here is a stupid question but...
Do you have the electronic AC or manual?
I ask this because I went to use mine a couple weeks back and got a lot of hot air in the face. I figured it just had to run a bit but still nothing. Eventually I tried the "AUTO" setting and wallaaa cold air again !! Maybe I need to read the owners manual or something since I never had one of these electronic controls before?

Worth a shot

[HPG]

Ok, thanks for all of the replies. It's an 88 with manual A/C. I checked the pressure in the low side, it was 70 lbs. Just in case, I added some R12 but that did nothing. I had 12VDC at the black and green wire going to the compressor. When I turned off the switch on the dash, the voltage went to 0. Back to 12 when I turned it on. I did ohm out the compressor and it did show a complete circuit. Don't know what the resistance should hve been. I can turn the outer half of the clutch by hand on the compressor. I have a friend who is a auto mechanic and will look at the problem for me. I'm just 5 week out of serious back surgery and can't do very much that requires bending over. Thanks to you who responded the the question.

[ashabazz]

With your gages on cycle the ac on and off if your gages move your compressor is working to compress the freon. 70 psi is about 70 degrees, you want your pressure to be about 35psi. I just finished repairing my a/c yesterday I recommend using freeze 12 it's cheaper and ozone friendly.