ehall

That's a good question. I can't imagine that you're doing it any harm if it's not being run. Is there oil in it? I would think that would be good to have in there, just to prevent corrosion. BUT...I'm just making educated guesses. I don't actually know the answer to your question.

ehall

bump

I'd still like to get as much edecated info, in this thread, as possible,

dacula951

What oil and refrigerant was in there Sept 2000? What do you mean by conversion kit? Does it include a new compressor? Do you know what caused the system to empty out?

When a system is empty and not tight, there'll be a small amount of air exchange during each heat cycle of the engine compartment. Air means moisture, and this moisture will have some effect over a long period of time. How much effect is difficult to say, but the longer the period of time the more effect it will have.

At the very least you will need to replace the filter/dryer and vacuum the system really well (not with one of those compressed air vacuum pumps but with one that gets down to the micron level of vacuum - very important for removing moisture). If you'll be retrofitting to R134a, I would suggest draining the old mineral oil from the compressor. If there's already been a R134a refrigerant oil added to the system, then you almost certainly have oil that has taken on moisture ( the R134a oils absorb moisture just as brake fluid does) and the system will need to be flushed to remove the contaminated oil.

mikeyoman

Plenty of basics in this free online course, not automotive per se but the principles are the same.

http://www.free-ed.net/free-ed/MechT...on/default.asp

site also hosts other courses covering loads of topics, anyone wanna be a Lawyer !

chrly924s

Two of us here each got these from HF. They worked great and were very inexpensive.


http://www.harborfreight.com/cpi/cta...emnumber=96677
http://www.harborfreight.com/cpi/cta...emnumber=92649

ehall

good stuff guys. Now I just wish that I had an air compressor, so I could pull a vaccuum.

dacula951

NO, not the compressed air vacuum pump!

As I said earlier, you really want a vacuum pump capable of producing a deep vacuum and those compressed air vacuum pumps don't do the job. Moisture is the enemy of a refrigeration system and a deep vacuum is needed to remove it completely. As you can see by the specs, it only pulls 28.3" of mercury. If you look at the chart here (some other good info on this page as well) you will see at that level of vacuum water boils somewhere between 86 and 104 degrees F. That means the entire system would have to be above that temperature to guarantee vaporization of all moisture (and there's a cooling effect that occurs when moisture evaporates). You would have to have the vehicle in a warm environment and run the compressed air vacuum pump for a long time to guarantee all the moisture has turned to vapor. Then beyond that, the vapor will be the last to exit the system, so the gases left behind by the vacuum that isn't deep will consist largely of water vapor.

It may be OK (although I still wouldn't use it) on a system that had a quick repair during which moisture had little chance to enter the system, but not for a system that's been low or empty of refrigerant for an extended period.

chrly924s

I wouldn't want to use this for anything as involved as an open system or extended low charge either. But for $15 I just got it to see if I could determine how bad a leak was on my wife's 928. A really good pump runs hundreds of $$. This would not pull a deep vacuum and hold it.

jwlester

It seems that sometime back I was looking at a site that sold rebuilt and new compressors for R12. They had some new compressor that required a mounting bracket similar to the Kuehl (sp?) compressor but it was for R12. Seems it ran about $300. I thought it might be Griffith's but I dont see anything. It seems that they may have also sold some of the R12 "alternatives" and I don't see that on Griffith's. Anyone have any idea who might sell the above items. I have a source of R12 and would like to replace my compressor, dryier, and anything else that is found lacking before I refill. I have an extra compressor that I could rebuild but I thought maybe there was a better alternative out there. Thanks in advance.

Cheers, Josh

dacula951

Actually, using vacuum is poor for finding all but large leaks. The deepest vacuum is only equivalent to about 14 psi and is the reverse direction of what the system will be operating under. Also, if there is any remaining refrigerant disolved in the oil it will slowly boil out under the vacuum and you may get a false positive for leak detection.

My favorite method for determining if a leak is present is by pressurizing with dry nitrogen. For nitrogen testing, you need to get ahold of a bottle of compressed nitrogen. They're available for about $85. Then you'll need a regulator to regulate it down. If you have an oxy/acetylene torch you can adapt the oxygen regulator. You can then connect the output of the regulator to your manifold guage set. Fill it up to 100 psi or so and let it sit overnight. If the temperature of everything is stable you should see no loss in PSI.

A dry nitrogen setup is also very good for purging the system prior to and while vacuuming the system. You can vacuum it down, fill back up to zero pressure with nitrogen, then vacuum down again. This ensures good removal of moisture.

I realize all this stuff costs money. Just trying to convey what it takes to do the job right.


I think these days you will not find a compressor that specifically says it is for R12. It will still work with R12. In may mean however that it ships with an oil that is compatible with R134a (PAG or POE). While POE will work with R12, mineral oil is much prefered so you'll want to drain the oil out of the new compressor. I would also suggest flushing it a bit with mineral oil (pour some in, turn the compressor by hand, then drain it out again) prior to adding the final amount of mineral oil.

jwlester

Understood. I realize the pump isn't specific to R12. I guess the real question is (and this might be question that helps more people than just me) who knows of a good source for new and reman compressors other than Griffith and the Kuehl compressor they sell? I know there has to be a better option than trying to reman one of the extra compressors I have.

Cheers, Josh

jwlester

PS....maybe this should get a sticky. I wonder if we could even talk our wonderful moderators into cutting some of the fat off this thread once it gets bogged down so just the valid questions/answers/resources are left.

Josh

ehall

good question. Let's let it go a bit more and I'll ask about a sticky.

PEvans

What is "the R134a conversion" for a 951?

Theo951

To your question on "what other refrigerants are compatible with R12" I can say for sure that I am running over 3 years the R-413A (Isceon 49) which is a mixture of R-134a/R-218/R-600a.
I got excellent cooling temp all the summers as use to have with R12.
Tricky part is evacuate the rest of R12 (if any left) & using the existing mineral oil in the system you add the R-413A. It is quite easy to find in Germany on web stores, cause is used on some Refrigerators and few AC house systems.
Two thinks to remember before you go for it. Make sure to replace your 20 years old (leaking internally) Heat control valve & make sure to add the right amount of new R-413A.
I can not recall what the conversion was, but I used approx 100 gr less than R12.
Not google stories, just my 951 set up today on AC.
Good luck