Hello I have an 1982 gmc pickup, half ton 2 wheel drive. I need to replace the a/c system on it. Condenser, drier, evaporator etc. I have the brackets for the small a/c compressor does the driver side. (Pancake compressor as i call it) what I need to know is what hoses and condenser and evaporator to I need? Do I get the parts for an 1982 , or do I need to get all the parts for a 1987 since that’s the year they had those compressors on?
any help would be appreciated.

 

You have an R-4 A/C compressor. Actually the big A-6 compressor wasn't all that great, IMO. Since you have an R-12 "Freon" system", you'll need to flush all the old mineral oil out, since that is not at all compatible with the R-134A.

You'll need a new "accumulator", but I doubt you'll need to replace the evaporator under the dash. Yeah, a new condenser, would be cheap insurance, and you need to install a new A/C Orifice Tube anyhow, as well as the low-high adapters for R-134A. Not sure which PAG oil you should use, but it will be PAG-46, or more likely PAG-150. That's what I've used.

Pump it all down to minus -30 PSI for half an hour, looking for leaks in the vacuum. A Couple of cans of R-134A should be enough. I don't use the refrigerant weight method at all, just the PSI A/C gauge set. Once it's blowing less than 45 degrees, it's a win-win with an old R-12 system.

 

There is a recommendation to change the hoses to a nylon interior barrier type. The reason was the molecules of R134A were smaller than those of R12 and the 134 managed to leak out. You might want to verify this with a good A/C shop..

 

Not needed at all.

I've done a couple of change-overs from R-12 systems. None of the R-134A, has leaked out to my knowledge. It is important to get as much of the mineral oil out with a good flush, dump the condenser, I'd like it if the compressor was replaced as that's where much of the A/C lubricant is located, but the flush should take care of it. I've gotten them down to 42/43 F at the center outlet, which is pretty good, but it takes some extra time to do it properly,

That ain't bad but I can get a stock R-134A system to 38 F. However they come with a system made for R-134A, including larger evaporator and condenser.units, as well. Just did my 98 K-1500, a few months go,as it had a bad low-side schrader inlet valve, seeping the green dye I put into it years ago. She was putting out 38 F when I got done. Added an once of PAG-150 too. Luckily, I have a good shop I use, when I need a hoist, to pull the R-134A out.