I would appreciate some help about where to start troubleshooting the almost-working A/C of a 71 Riviera. It blows cool, but the clutch pulls and releases the compressor in about 3 second periods, on, off, on, off... If one listens very carefully in park without any road noise, it sounds like there would be an alien breathing slowly inside the A/C duct... uzzled: Have had the car only for one week so far and I do not know when was the last time the A/C had maintenance, but at least the POA valve has been replaced somewhat recently (= it looks new) I must convert the system anyway to R134A since R12 is not legal here, but not much sense in trying that before I find out if there are some 'issues' in the system today. Not to mention aliens! :laugh:
Low refrigerant is the first thing that comes to mind. Know anyone with a manifold & gages that can check it for you for low dollars? I'm not sure how likely you are to find someone with the right tools over there. Devon
Markus, I would agree with Devon that your symptoms sound like a low charge of refrigerant. Before you convert to R134, you may want to consider Duracool since it is compatible with R12 oil but you would have to change ALL the o-rings to the new high tech green material. It works great, is about 40% more efficient than R134 and a lot cheaper than R12. You would have to check on the legality where you are but it is supposed to be environmentally friendly, non corrosive, work at lower pressures and has a higher flash point. I was skeptical but it does work very well. Let us know what happens. Regards, Arland
Thanks for the great replies! :TU: Devon; yes, I have to check the amount of refrigerant in the system. There are A/C shops nearby, but I have to ask around if any of the shops handle vintage systems too. Arland; thanks for the tip on Duracool! I'll use the phone tomorrow to check what R-12 substitutes are available before attempting a conversion. Would be happier to find a substitute! Andy; I have the manual A/C. Scott; yes, a very good question! I did some checking and noticed that I indeed have a "POA upgrade kit" from Old Air Products installed. I checked their website, but did not find any info whether this upgrade kit is the cycling type or not. Is it possible to recognize the difference from what the POA valve looks like (see photo)? Started to think about the word "upgrade"... Looks like the original type POA valve costs multiple times more than this "upgrade" kit. Is it so that controlling the system by cycling the compressor clutch makes it possible to use a more simple (cheaper) POA valve, or what is the real idea behind the cycling POA? uzzled: Cycling does not sound like an "upgrade" considering the compressor and clutch...?
Yeah, that's the problem with all these add-on kits & conversions. The clutch was never designed to cycle & causes the clutch to wear out prematurely. The POA valve metered the amount of freon going into the evaporator to keep the system from freezing with the compressor always running. The Dura-Cool is a reasonable alternative, but also has it's drawbacks, like 80 some percent is 134A. With R12 & R22 mixed in along with some propane.
Marcus, since you have the CYCLING CLUTCH ORIFICE TUBE (CCOT), you now know why your compressor is going on and off and don't need the wiring diagram. Like it was said above, it's low on refrigerant. I bet it has already been converted to R134a and now has a leak . To fix it correctly, you fix the leak and then recharge.:TU:
Well lucky me... I like the original style system better and did not think that someone could have already "upgraded" it... I know that I should not complain; if fixing a leak is the only thing that needs to be done, things could be worse. However, I do miss the old style POA valve the other Riv has. No cycling...
telriv, There's no R-134a in Duracool. -Duracool is a Hydrocarbon refrigerant (propane, butane, etc) blend. (I hear it works very well, but I'm not a fan). -Freeze 12 is 80% r134a blended with R142b to carry the old R12 mineral oil. -There are a couple of alternates out there that contain R22, but they're not very popular and are seldom mentioned. (R22 is hell on rubber and needs metal lines). marvi, If you choose an alternate refrigerant, do some homework first. There is NO "drop-in" replacement for R12. Each requires specific system alterations or procedures to work well and correctly, regardless of the manufacturers marketing hype. Some more than others, but none are "drop in". HCs are close but they have drawbacks and getting the charge right can be tricky. (nailheadina67 is the resident Duracool guru, he can hook you up with info) Those POA valve update kits are actually a "downgrade" for the POA system on 60-70s GM cars. They are popular because many people are intimidated by the POA valve, they don't understand it. It makes the system operate much like the cycling clutch\orifice tube systems of today. If you can locate a good POA valve, I would suggest putting one back on your car and adjusting it for R134a. It's a simple procedure and the system will work like it should. Good Luck Here's my usual POA valve rant (Not necessary reading): The Frigidaire designed AC system in 60-70s GM vehicles is considered by MVAC (Mobile Vehicle Air Conditioning) professionals to be the best MVAC system ever made to date. The A-6 compressor had the displacement of a small lawn mower engine and the POA valve would throttle the evaporator pressure to a point where vent temps could actually get below 32 degrees F in all but the highest temperature/low humidity climates. Any "modern upgrades" would be a "downgrade" to that system if you are looking solely for AC performance. (usual rant off)
