Hey everybody, The air con on my '72 Riviera is not currently working. There are clearly some issues with the vents as the top ones are not working and I believe there could be vacuum leak. Putting that to one side for the moment, I wanted to just try and recommission the air con and make sure it is functioning correctly under the hood. I have her booked in with 1 guy who said that he will have a look and do what he can. Others have emailed back and said they cannot help. Has anybody had recent experience and success with recommissioning their air con?
There is a vacuum storage container on the firewall. It is fed with a single vacuum line from the back of the carburetor usually. There is also a thin vacuum line exiting the storage container going into the firewall to the instrument panel. The vacuum is used to move climate control doors. Check the storage container for leaks or missing vacuum lines.
Under the hood, its pretty simple - pull a vacuum and wait....then fill with freon(if there are no leaks). Any old school AC tech can do it in their sleep. However, most old school guys have retired, EPA has put the squeeze on AC work, and lastly and most importantly you cannot use the freon from 1972 (with a few exceptions). So, the system needs to be converted to freon 134 by changing the seals and cleaning the system. Look on line for the steps. If you have someone who will try - great. Since you are in the UK there may be more or different issues, but you get the idea!
I work in portable refrigeration and we ( the boss- I do the donkey work!) always a pressure check with nitrogen before evacuating and gassing the system. I don't know how relevant that is, thought I'd mention it. We'd rather loose some nitrogen than expensive refrigerant.
Thanks for the advice. The guy I am taking it to said he would pressure test after he has had a visual inspection and thinks he can help.
The first step I'd do is check the clutch (electric) on the front of the compressor for function. With the engine shut off, you should be able to turn the smaller diameter hub in front of the clutch to make sure the compressor is not locked up. Next start the engine and turn the AC on. The clutch should engage and spin the smaller part in the front. Thatll prove the clutch, electrics and compressor. The compressor should run on AC, MAX AC (recirc?), and DEFROST. Next up would be a vacuum test. Nitrogen works as well for a pressure test, but the vacuum should pull down to about 24 inches (In Hg). Turn the pump off and it should hold the vacuum almost indefinitely (in a perfect world). If you lose one inch of vacuum over 24 hours thats probably OK. Five inches or zero means the comp. seal is bad. If you have access to R12 freon fill it to about 3-3/4 lbs (its on the compressor label). I converted mine to R134A which means changing the oil in the compressor, replacing the filter drier, and recalibrating the POA valve, plus CLEANING EVERY DARN THING in the line; hoses, condenser. evaporator and changing the O rings. The esther oil is not at all compatible with mineral oil. . Its all about heat and pressure. https://www.google.com/search?sourc...hUKEwie-MjZ493jAhVRTd8KHVQ0BN4Q4dUDCAc&uact=5 Find an old timer thats done work on the old stuff if youre not sure. Its really not magic, more like knowing whats what. Grab a seat in the loo (!!) with a bright light and read and re-read the AC section in the shop manual. Itll walk you through step by step. All the controls inside the cabin are electric and pneumatic (pressure and vacuum) for the door controls and hot water to the core controls. If you need to pull the control head off, be easy! The hoses are stuck pretty well and the plastic is really brittle and made of almostunobtanium! Mark the hoses with a tag of masking tape so they do not get mixed up. If you have a "Climatrol" system (auto temp control), all bets are off LOL. Again, follow the instructions ver batum! Good luck Gubnah! Maybe youll get lucky! ws
I am in the process of rebuilding my ac system right now. I am in New Zealand. I found a long-established radiator and ac shop to leak test and flush my evaporator and condenser cores. I am rebuilding my compressor myself....almost finished. I am waiting on a new bearing to arrive. I will be converting to 134a. I haven't decided if I will rebuild my original hoses (retain original fittings) or go with new reduced barrier hoses. I was intimidated by restoring the ac system until I did some reading. I am having fun with it! Under dash heater box already restored, working on the blower housing and evaporator box as well. I guess in summary, a long way of saying good luck, have fun, and like Bill said...do your homework. Disclaimer: I have a 67 GS.
Oh my! Well thanks so much guys! Ed - good to hear you are doing that stuff yourself, really admire you. I will have a read up. Bill -thanks so much for all of the detailed info, especially about the almostunobtanium! I will make sure that the air con guy knows about that if they get to that stage. I think you're right, a guy who has worked on these before would be ideal. I am going to message a guy I know in the UK with a '72 Riviera and see if he has had his air con worked on.
Bit of an update, a guy has replied to one of my messages. He said that he can come out and see me and that he works on American cars a lot. Fingers crossed he can help!
A couple of things - Air conditioning systems usually have a low-pressure cutoff switch. If the system is low on freon the compressor will not engage. To check the clutch you will have to bypass the switch. Second, Older GM systems used what was called a Thermal limiter located near the compressor clutch. They were famous for burning out (a thermal limiter works like a fuse). The comment was made earlier that to convert to R134A you have to replace the seals; I'm hoping that he means the O rings, the front compressor seal is ceramic and doesn't care what kind of refrigerant is in the system. I converted the AC system in the Buchev to 134A when I installed the engine about 10 years ago and it still blows cold. I would get a vacuum diagram and go over every inch of the vacuum system. This is a stinking job, but I don't recall ever seeing a GM vacuum system that is north of 40 years old, that doesn't leak somewhere.
The pressure cut off was after the super heat switch. Those were a pistol to change. The pressure cut out took care of that. The PS came in around the time of the radial compressors. Thats mounted up around the POA device IIRC... That switch made pressure diagnosis easier to find if you needed to run the compressor while low on freon. I also believe the compressor takes an O ring seal behind the mechanical seal to keep the ceramic face and clutch faces clean from oil. But yes, I was referring to the O rings on the connections. ws
Gnatsum, Found this stash of Riviera parts. he might have the under dash panel you seek! https://www.teambuick.com/community/index.php?classifieds/assorted-buick-parts.13/ Gary
Hi Bill, When the Buchev was converted to 134A, the engine had just been replaced; I knew that if I didn't do the AC at the same time (a fairly big job because although the truck had AC the 66 Buick Electra Nailhead that I used didn't). I had to find all of the various brackets and pulleys to install the compressor on the engine. The hoses connecting the compressor to the truck were custom-fabricated,; I told the guy who made the hoses that the system would be running 134A so he installed the proper O rings. I purchased a new A6 compressor well after 134A had come into widespread use, so I'm hoping that any seals and/or O rings in it are compatible with the newer refrigerant. In any event, after a decade it's still working great and not leaking. If I ever have a compressor issue, I will install a direct-replacement Sanden. I am told that they use far less power and I know that they are a lot lighter. The huge old A-6 is still a hell of a compressor, thoiugh.
