I posted this in the wrong place the first time so I'll do it again. My '78 came with no belt on the compressor so I figured the compressor was shot or something else. Tonight I hooked up a vacuum pump up to the fittings and pulled it down to 28" and it dropped 1" in 15 minutes. I put a belt on and listened for any bad noises - none heard. Will the compressor clutch engage with a vacuum on it or will the pressure switch on the back of the compressor affect it? I do have power to the coil.

Nope, clutch will not engage without at least a little bit of charge.

Good enuff. I'll put a little R-12 in and see what happens. Thanks, buddy!

Be sure you can rotate the compressor by hand before you put any R12 in it. Don't waste the R12, cost to much.

Don't run that compressor very long without a proper freon and oil charge. A compressor has bearings and pistons (or vanes) and needs the oil for lubrication. You might want to do a R134A conversion--R12 is very expensive and hard to get.

What kind of things will I need to convert to R-134A? I've seen the kits at Advanced Auto for around $35. Seems kind of cheap for some reason.

What kind of things will I need to convert to R-134A? I've seen the kits at Advanced Auto for around $35. Seems kind of cheap for some reason.

The reason it seems cheap is because it is cheap, and not recommended.
We in the industry call these "suicide" kits.

The kits usually consist of a pair of service port adapters, a can or two of refrigerant, maybe a can of oil, and a short little hose and a can tap.

You will need the adapters, oil and refrigerant for sure, but to do the job correctly, (at a minimum,) you will need to flush the system, replace the accumulator/drier, evacuate the air from the system with a vacuum pump and, using a set of a/c gauges, charge the system with 80% of the original R-12 charge, with 134a.

There are several variables that come into play when doing a/c service, and it is VITAL to to your own SAFETY, and operation of the system to know EXACTLY what the pressures are in both sides of the system when charging or servicing the system.

I repair a/c systems all summer long that have been damaged by incorrectly attempted conversions. Many of these customers could have saved themselves hundreds of dollars by having the job done correctly in the first place.

Save yourself the headaches and heartaches by taking the time to understand the operation and servicing of the system before you attempt to service it, or take it to an a/c shop.

Acauth 1 gives good advice. You can do the conversion yourself, I have done several sucessfully and I am not the professional that Acauth 1 is.
As long as you don't do anything unsafe what do you have to lose? the A/C isn't working now anyway. There should be a store near you that specializes in automotive A/C supplies and tools--they should have the flush, oil, fittings and all the replacement parts you need. Since you already pulled a vacumn you have a pump and guage set. If you only lost 1 inch of mercury in 15 minites it seems like you don't have any leaks. Go for it.

Well, the bearing bit the big one yesterday on the way home from work. Having a vacuum in it didn't kill it because I never turned on the AC or DEF. I'll cabbage one off of my other one and stick it on the '78 - I know it is in good shape because I replaced it about 4 years ago and it works.

I have a guy at work that has gauges to do R-12 and I let him do my recharge. I went to tech school and learned how the system works but it's been so long and I don't do it all the time I have forgotten how much pressure each side needs so I just let him do it. He's also been to school, too.

Here's a little article I wrote a while back:
http://elcaminocentral.com/article52.html&mode=thread&order=1&thold=1

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