Just got back from my 1400 mile drive home from Chicago with the new toy, my 1978 Silver Anniversary Vette.  A few minor things need to be fixed, one being the A/C system.  I've just had it converted to R134a, but we found a blockage at the orifice (spelled correctly?) valve.  The compressor was running so hot that it actually burned the tech charging the system.  Ssssoooo... guess it's time for a new compressor, dryer/accumulator, and orifice valve.  Now comes problem #1: how do I tell what type of compressor it is?  Is there some way to identify a R4 or A6 compressor? 

After I replace that, my problem #2 will be related to the ammount/type of oil and refegierant I'll need to complete the fix, but I'll worry about that once I replace the compressor, etc!

Scrap that question about the compressor type... just found on Advance Auto Part's site a pic of my existing compressor, definatly an R4.  Looks like Advance Auto has a decent price too.. $132 for the compressor, orifice tube, and "rec. dryer".  Guess I'll be taking a drive over there soon.

the long compressor is the A-6 and the short one is the R-4, a little friendley advice, don't buy a rebuilt unit, of the two GM compressors the R-4 was the weakest the A-6 was the best when new, rebuilt A-4's are plain junk, that the word I get from my AC bud's, you don't want to do the job twice.

Thanks for the advice.  However, the 'new' rebuilt R4 is already bought and installed...guess I should of bought a spanner wrench when I got the a/c stuff!  Right now I'm waiting for a friend to drop off a spanner wrench, then recharge the system, and will wait with anticipation for the cold air to arrive!

Just make sure there is enough oil in the system.  There is no oil pump or reservoir in the R-4 compressor.  The oil is circulated by the freon.  If it's low on oil, it will run hot, even with the proper amount of freon.

Ken, good to see you back on line, ya know this Forum is really go for everyone, Yes, I agree with ken.

Thanks for the heads up kstyer.  I found that some of the oil comes out while installing the compressor, but it came with a little oil in it too.  I figured I'll use the R-134a that has some oil in it to compensate for the lost oil.

Wish I'd had the chance to chat with you guys before I jumped into this A/C project.  The old compressor was also a rebuilt one, and I let a local shop convert the system to R-134a from R-12.  If I'd done some of my own investigateing, I'd of seen that the entire retro fit and recharge kit is only $40 at Advanced Auto.  Oh well, lesson learned.... Now on to the universial joint and tirod....

i had my 77 vette's a/c system rebuilt about 2 yrs. ago. a problem i am having is the a/c belt flopping. yesterday i had another belt installed with the length shortened by an inch. this made the problem better but not completely correct. my mechanic say i might have to have the compressor replaced.does anyone else have this problem. thanks, gene (ge77vet)

sorry folks, thats (gs77vet) gene

[QUOTE=Lockdown]

Thanks for the heads up kstyer.  I found that some of the oil comes out while installing the compressor, but it came with a little oil in it too.  I figured I'll use the R-134a that has some oil in it to compensate for the lost oil.

Wish I'd had the chance to chat with you guys before I jumped into this A/C project.  The old compressor was also a rebuilt one, and I let a local shop convert the system to R-134a from R-12.  If I'd done some of my own investigateing, I'd of seen that the entire retro fit and recharge kit is only $40 at Advanced Auto.  Oh well, lesson learned.... Now on to the universial joint and tirod....

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 Buy a can of Ester Oil and dump it in the compressor before you install it. Also, turn the compressor a (Not the pulley) about 10-12 times to get some of the oil on the pistons. Lessons learned the hard way !