Constant On Air Conditioning Compressor

[Grizzly]

Trying to help a friend with a 74 stop the a/c compressor from running all the time. Where should we start?

What is the best way to disable it without damaging it if it is not an easy fix?

 

[Ken]

What is the best way to disable it without damaging it if it is not an easy fix?

Pull the fuse.

 

[MaineShark]

I don't know about '74, but in my '79, the A/C fuse appears to power the whole climate control system.

You can always disconnect the plug from the A/C clutch, though. Right behind the pulley.

You can also remove the belt, if you feel the desire...

Joe

 

[CS72Roadster]

Sounds like the low pressure switch may be out of adjustment. Follow the green wire from the compressor clutch back and it should lead you to a switch on the POA valve. If you unplug the wire at the switch, the compressor should stop. There is a screw in there that regulates when the compressor kicks on and off. You may need a new low pressure switch. It screws off of the POA valve.

CS

 

[Stallion]

Maybe it's the solenoid? I would disconnect it, but then it wouldn't run at all. I think CS might be right, it could be the low pressure switch. I would try that first.

 

[MaineShark]

I'm pretty sure that the low pressure switch can only prevent the compressor from running, not force it to run all the time...

Joe

 

[CS72Roadster]

In fact it can, if it is out of adjustment and the setting is extremely low. While workling on my a/c earlier this week, I had the compressor running with the low pressure switch completely off of the POA valve, but connected to the wiring. You can also unplug the wire from it and using a jumper in the plug-in connection make the compressor run continuously. A faulty switch could do the same thing.

Keep in mind that the low pressure switch is adjustable and may have to be adjusted depending on what type of refrigerant you are using. Mine is charged with r416a and requires around 23-28 psi on the low side for optimum cooling. r134a will need about 30-32 psi. The switch adjustment will be different for these two refrigerants.

It is a possibility. I would check it first.

CS

 

[Stingray6974]

Hi all,
The '74 doesn't use an adjustable low pressure switch. It's a V.I.R. system designed to keep the compressor running all the time when the AC is turned on. If the compressor is still on when in the heat position you probably have a broken ac switch in the console attached to the thumbwheel. When it breaks the compressor stays turned on.

Mike

 

[CS72Roadster]

Ahhhh. Sorry, I didn't think about that being different.

CS

 

[Lee74C3]

Stingray6974 is on target. I have just finished months of work to rebuild/replace AC components on my '74 Coupe. If Grizzly's friend just wants to stop the compressor from running at all times... just pull the plug at the rear of the compressor or either terminal (both green wires) off the low pressure switch. The switch is attached to the right fender just under the lip and forward of the radiator overflow tank.

The compressor should run all of the time in the following modes, AC Max, AC Normal, Bi-Level, and Defrost.

If it is running in vent or heat, my guess is the switch is worn-out or failed, or an electrical short that provides current all of the time.

Who know's... maybe Bubba has visited this guys car?

ps - I stayed with R12. It is nice to have a very cold AC system again.

 

[Stallion]

I don't even use my AC. The only cooling I use it 260 cooling. 2 windows open, going 60 miles per hour. I love the feel of the fresh air. Especially with the t-tops off.

Which is the illegal kind that's hard to get? Is it R12?

 

[MaineShark]

Which is the illegal kind that's hard to get? Is it R12?

R12 isn't completely illegal, yet. Just expensive and tightly-regulated. There are enough R12 cars on the road, right now, that there can't be an outright ban on R12 without an uproar. Give it 10 years, though, and R12 will probably get the axe, or get so expensive that no one can afford it.

Joe

 

[Stallion]

Then what are us C3ers going to do? Is there any other that is compatible with our AC systems?

 

[CQRT]

Fan clutch may be hanging up - - - I had the reverse problem of getting it to engage . . it's the disc on the front of the compressor and is spring shimmed - - just behind the pulley......apparently a common ailment on the older cars.
Regards-
RWT

 

[CS72Roadster]

You can buy r12 on ebay all day long. All you need to do is, take the section 609 certification test. You can do it online for 15 bucks. Anyone can do it and with that certification you can buy any type of freon. R12 on ebay runs around 15 -20 bucks a can.

CS

 

[Ludigdrums]

The compressor should run all of the time in the following modes, AC Max, AC Normal, Bi-Level, and Defrost.

Is this also true for an 81?! I started a thread about this... http://www.corvetteactioncenter.com/forums/showthread.php?s=&threadid=34209&perpage=15&pagenumber=1

Mine stays on all the time, although I thought it should cycle?

Seems everyones saying something different..what gives?!

Thanks!
- Jeremy

 

[JohnZ]

If you have a cycling system, it will explain that in the "Climate Control" section of the owner's manual.

 

[Stingray6974]

Late '76 to 82 C3 use the R4 compressor and accumulator. The expansion valve was replace with a fixed orfice tube and the POA valve was eliminated. The compressor is contrtolled by a low pressure cycle switch on the accumlator to keep the system from freezing up.

Mike