AC compressor help

[Gary N.]

I have the original A-6 AC compressor on my 66' Coupe. It was working fine until this weekend. I got caught in traffic and the engine temp started to get hot, so I shut off the AC. By the time I got out of the traffic I noticed white smoke coming from under the hood (thought it had overheated). I pulled off into a gas station and opened the hood and there was smoke coming from the front of the compressor. I let it cool off some and decided to take off the AC belt to get to where I was going. I thought that the compressor might have locked up. I was puzzled because I thought that I had shut off the AC earlier. Later that evening I looked at the compressor and was able to turn the front of the clutch by hand, so I don't believe it was locked-up. I'm now wondering if the clutch has gone bad. I know that the clutch is magnetic, but how does it operate (it can't be metal to metal)? Is there a material similar to a clutch plate for a transmission that could have been slipping and overheated? I am justing trying to look at all options before I decide to take the compressor off and replace it or have it rebuilt. I don't believe that I have lost any freon because the system was working fine up until that point. I will double check it tonight. Can the clutch be changed on the car and not disturb the freon, if necessary?

[Jim T.]

Re: AC compressor help

The clutch/bearing can be changed without losing R12.

[Larry M.]

Re: AC compressor help

The clutch/bearing can be changed without losing R12.

Agree with Jim, unless you have extensive damage to the bearing and/or shaft. Special tools are required, but can be purchased. Auto Zone may have loaners or tools that can be rented. You will need a puller, a special tool to hold the clutch steady to remove the front shaft nut, and an installer. Possibly brass (non-magnetic) feeler gages. These are also available.

The Chevrolet Service Manual has an excellent section on air conditioning repair. Recommend getting it if you do not already have.

I had a similar problem on my 1978 Z/28 with A-6 compressor. Bearing froze up and I had to cut the belt to continue driving. Later replaced with no issue or freon loss.

Larry

[Gary N.]

Re: AC compressor help

Larry,
I take it that you were able to do this yourself?

[Larry M.]

Re: AC compressor help

Larry,
I take it that you were able to do this yourself?

Gary:

At that time (many years ago) I took the car into a local auto repair shop for this repair. Took only about 45 minutes, so I waited and watched.

Yes, with tools and knowledge I have now, I can do this repair on my 1967 Corvette with factory AC. But I hope it doesn't happen to soon

Larry

[Wayne M.]

Re: AC compressor help

,.. so I shut off the AC. By the time I got out of the traffic I noticed white smoke coming from under the hood (thought it had overheated). I pulled off into a gas station and opened the hood and there was smoke coming from the front of the compressor. I let it cool off some and decided to take off the AC belt to get to where I was going. I thought that the compressor might have locked up. I was puzzled because I thought that I had shut off the AC earlier. Later that evening I looked at the compressor and was able to turn the front of the clutch by hand, so I don't believe it was locked-up. I'm now wondering if the clutch has gone bad. I know that the clutch is magnetic, but how does it operate (it can't be metal to metal)? Is there a material similar to a clutch plate for a transmission that could have been slipping and overheated? I am justing trying to look at all options before I decide to take the compressor off and replace it or have it rebuilt. I don't believe that I have lost any freon because the system was working fine up until that point. I will double check it tonight. Can the clutch be changed on the car and not disturb the freon, if necessary?

Gary -- if you can turn the clutch hub by hand, probably the compressor is OK, and it was just a pulley bearing failure. Even though you turned off the A/C, the pulley (which is free-wheeling on the pulley bearing which is press fit on the stationary nose of the front head of the compressor body) still rotates, acting as an idler for the A/C and water pump belt.

Pic below might help visualize. You can see the square "key" resting on the surface that the pulley bearing presses onto. The pulley install/removal tool is shown threaded onto the shaft of the compressor. You can see the matching keyway in the clutch. Neither bearing or pulley show in this shot -- ignore the visual pollution of the T.I. distrib stuff.

[Gary N.]

Re: AC compressor help

Wayne,
The strange thing is that the pulley still seems to rotate freely when the clutch is disingaged and as I said I can rotate the front hub of the clutch by hand. If it was the bearing I would think that it would not rotate freely, that's why I asked if the clutch could slip against something when engaged and be heating up. The compressor did sling some oil when you first started it up, but would stop after it ran a short while. I checked and the system still seems to be full of freon when I tried to let some out of the schrader valve.

[Mike G.]

Clutch Clearance Gap

This is worth checking to make sure it's not too tight. I'm thinking that it might have closed up due to heat and then you got friction burn as the surfaces spun. Just one possibility to eliminate.

Increasing the gap is easy with the clutch puller tool. You shouldn't even need to loosen the nut. Check the manual for the spec but I'm recalling it to be around .045".