I have a 72 vette (duhh) which has a strange AC problem. I just had it serviced with new lines and compressor. It is fully charged. The guy that done it has numerous years of service with AC problems - he remembers these cars when they were new and worked on them! The problem is that the compressor will not engage from time to time. It has no loose wires that we cn find. the switch on the controls seems good. He jumped it with a hot wire and it now works properly. It worked fine a couple of weeks ago and then stopped but it just started working again. When it stops the clutch seems to be trying to engage but it does not seem to have enough juice to do so. He thought it might be a relay that is shown in his manuel. I think it was a anti deseling relay--It shows to be in the AC Circuit in his Chilton's but my 72 chevy maneul does not show that. Does anyone have any idea of what to look for. He is completely out of ideas. He said this one has him stumped and he refused to charge me for working on it all day! He said if I can come up with a idea he will give it another go. We check a relay behind the dash which did not have any impact on the AC--do not know what it was. I would be most appreciative if anyone has some ideas. i have owned this car since the 70's and I would like to drive it more. :flag

 

The only way to solve electrical problems effectively is to check voltage. Start at the plug on the compressor. Does it have 12 volts at those two wires when it acts up?

 

It is possible from normal wear the distance between the clutch plate and pulley has worn enough to prevent pull-in. The fix for this would be to draw the clutch plate in (using the clutch installation tool) until you get to OEM specs. If it won't draw in far enough you probably need a new clutch. I think the specs call for .032" of clearance on the A6 compressor.

 

Have you taken your manual to him? I have a service manual for 1972 that has all cars in it. The Corvette air is covered in the heater, etc section #1A. The relay? may actually be the ambient temperture switch. My schematic is on page 1A-66.

:seeya

 

My '71 does have an anti-dieseling relay. Yes, it is behind the passenger side dash, bolted to the big plastic housing that holds the heater core.

 

Thanks for the help. Yes the clutch is within spec's, and we have used a volt meter on the connection at the compressor. It reads twelve, but it does not seem to have the current needed to pull it closed, if that makes sense. When it does not work the test light that I also use does not glow as bright as when it is working.
I looked at the chevy manuel and the chiltons as well. The chiltons is closer to the 73 version tht is shown in a parts book that I have. This car has some things that are closer to a 73 from what I remmeber in working on it in the past. The 73 book shows the anit desieling thing in the book as well as another relay.
I bought a new compress switch, but when I checked the old on it worked fine, with plenty of voltage coming out. Does anyone know where to get the rely for the anti deseling for the car? I guess I will replace it as it does not seem that hard to get to. Thanks--always open to otehr suggestions.