I've been reading this forum on and off, but haven't posted to it in quite awhile. I have a question about the A/C unit in my '70 SB Coupe. The car it very original and the a/c is original/untouched/ intact. But it has not blown cold air for about the last 24 years. I really never turn it on anymore but it is all there.
How should I go about putting the a/c in order? As I get older these things become more important than laying rubber. I am the only one that has turned a wrench on this car in 25 years, so i can still do that, but I never learned much about a/c. Any help much appreciated.

 

Do this first:

Determine if it has refrigerant in it. Try and vent a little from the low side fitting.

Determine if the compressor will engage.

More trouble shooting after you answer those questions.

 

Auto a/c is not something that can be properly worked on without knowledge of how these systems work or without much needed a/c tools. It's not like replacing a carb as mistakes can become quite costly including hurting yourself. I would have a pro look at it or take some classes on the subject. Just my 2 cents.

 

Odds are that you are not just going to be able to pull a vacuum on it, charge it up and have it work. The compressor is probably frozen, POA valve is likely gummed up, and you will need a new drier accumulator for sure. The evaporator core and condensor should be flushed out and leak tested. Hoses may be dry and cracked and need replacing also. The expansion valve may need replacing as well. All of the parts are available and fairly reasonably priced. If you replaced every piece of the plumbing and the compressor you can probably do it for around $1200 in parts. If your system has been closed up (not taken apart) all these years, I am guessing that the majority of it is reuseable. Get the Haynes book on automotive AC and study up on it. Buy some gauges, and do some diagnosis work. A little patience and you will have it blowing cool in no time.

 

After 25 years, I wont be surprised if you find a leak in compressor's shaft seals, a rubber hoses that would explode when you charge the system with gas, a stuck POA valve, a clogged expansion valve, and some other issues that may happen due to the age of the components. If you really want to preserve all the original components, I would at least disassemble everything and do a close inspection and pressure testing, then rebuild the compressor and buy new rubber hoses. Thats what I do with my '71 A/C and its been working fine for over a year now, and I knew nothing about A/C when I started it, just reading some books and having this forum.

 

Well my 71 coupe still has the original hoses, evap core, condensor, POA valve etc and all those work well, the only problems I have had was with the NEW compressors.

If I were you, I would hit the switch and see if the compressor comes on, if it does, then dump a can of R12 in it and see what it does, if it starts to cool down, then you know the components are working. Recharge to capacity and let it ride and see what happens. As long as its working, I wouldn't pull it apart until you have to.

When I first started messing with my AC, it had not been charged for 20 yrs. The compressor would come on and the fan would blow but thats it. We stuck a couple cans of Freeze12 in it(Don't use that though, use real R12) and my AC instantly was pumping 45* air out of the vents after not being used for 20+ years. That lasted about 2-3 months until the compressor blew the front seal. Had that not happened, it would have still been working well with all the original 1971 hardware.

See what you got first...you might get lucky. Get a good AC guy to throw 3 cans of R12 in it and see what happens. Might not be a bad idea to at least pull a vacuum on it first though. IF the system has been sealed up tight all these years, it may still be clean inside.

 

Thanks everyone for the info. I haven't done anything yet but just as memory serves: Yes the system has never been apart. And I do believe the compressor is engageing. That is one thing that I have worried about for sometime. The compressor comes on when I rotate the controls to the heat and defrost mode passing thru the a/c mode. Also, i believe the a/c is engaged when the defrost is on. I have worried that the compressor might lock up due to no lubrication. but so far it never has. One thing that I have never investigated yet should have is my air flow tubes and doors. I've had the dash apart a few times over the years to repair electrical issues, mostly burned out bulbs, but have never spent any time looking closely at the air routeing situation. My point is I get almost no air out of my vent outlets when engaging vent or a/c. But, my air control system is mostly working because the heat and defrost work perfectly. So I have no air flow and I don't believe I have any cold air. I will start to do some checks based on what you have told me. Thank-you.