SteveG

Anybody know where I can get adaptor so my r12 vacuum pump can pull a vacuum on a 134 system? the one that I think fits listed on ebay is a paypal account, which I don't use, and they don't return calls. The Robinair distributor w/i striking distance is out. Nothing is easy, at least not lately. I think the nipple coming out of the r12 manifold is 1/4", but the 134 hose that would attach to it is also a "male" threaded end, 5/16s(?).

Rob Edwards

Like this ? http://www.amazon.com/Robinair-ROB15.../dp/B0002T5BI0


If that isn't what you need, post the Ebay auction #, I'll buy it and have it shipped to you. Then you can mail it to me when you're done. I'll need one too, as I have an r134a pump with which I will need to evacuate my R12 system if I ever get around to re-o-ringing the system......

dr bob

Steve-- The pressure switch an dthe pressure transducers on the S4+ cars are threaded onto standard R-12 schraeder-valve ports. You won't need the transducer while evacuating, so disconnect the wires and unscrew the transducer. Hook your vacuum pump there, and get all your charging hoses attached all the way to the freon cannister. Run the vaccum pump, and it will suck all thje air out of the system as well as any air in the charging manifold and hoses, eliminating possible contamination. When you are ready to charge, unscrew the vacuum pum,p hose and replace the transducer. The schraeder valve underneath shouldl preserve your vacuum, but you may decide to put a little pressure into the system before you remove the hose, just in case that valve has trouble with vacuum. It's not a bad idea to put a new valve core in there before you even start, so you'll know the seal in the valve is good with R-134a and the new oil.

SteveG

Rob: Thanks for the offer. I'm going to try Dr. Bob's suggestion.

Bob: THAT is a tidbit I would not have thought of. How do you know this stuff?? That should get me through this weekend. Thanks. I will be checking freeze switch from a previous post of yours and then it is on to the orings underneath. Do you know if "stop leak" or whatever fouls the dryer? If you were working on this problem (probable leak showing stop leak failure (gummy stuff around connection)) would you flush, replace dryer and expan valve too?

Thanks.

dr bob

Steve--

I went through the same issues when I swapped to R-134a in my 928 so many years ago now. "Old" vacuum pump with R-12 hose connection, new charging manifold for R-134a, and of course new fittings for the car. I pulled the switch and transducer to update the valves under them, just to be sure. Obvious problem solved as soon as I saw how the switches attached. FWIW, this is a very common method of switch mounting, so that switches and such can be serviced without a full evacuate/recharge of the whole system.

On the stop-leak issue: I replaced the expansion valves and the drier as part of the conversion. The expansion valves are common to late BMW (and I'm sure other) cars, so the ones we get now are R-134a curved. The expansion valve is probably the most-likely victim of any possible stop-leak damage, but... AC stop leak isn't a goo that circulates in the system, it's more like the oil except that it stiffens some on contact with air. The reason that shops hate it is that it is carried by the gas not the oil when circulating, and it will foul their recovery equipment since it doesn't drop out in a coalescing filter as the oil does. Drier: The drier needs to be replaced whenever the system is opened anyway, but more important when changing to R-134a so you can get rid of the mineral oil that's soaking the dessicant bag, and get new dessicant in there that's compatible with the new oil and refrigerant. I used the aftermarket 944 drier (Parker IIRC), cheap at ~~$25 at the time, but just a hair smaller in diameter and a hair longer than the 928 drier. A shim in the bracket and a shield on the bottom made it work perfectly. Plus it has a sight glass, unlike some other replacements.

Use the polyolester oil, not the PAG, when updating refrigerants in a 928.