JHowell37

The normal operating pressures for R-134a are well within the limits for hardware designed to use R-12. At most there's a 10-20% increase in system pressures. R-134a will not cause system pressures so high as to cause an equipment malfunction under normal circumstances. Those pressures that caused equipment failures were a result of other problems such as blocked condenser, malfunctioning expansion valve, overcharging, overcharging with excessive air and moisture in the system, general mechanical incompetence when retrofitting systems.

I'm not up for searching for any links tonight.

I sometimes wonder if the real reason people are so against R-134a is because they feel emasculated by using something deemed "environmentally friendly." My dick didn't get any smaller when I charged my car with R-134a.

hacker-pschorr

I have a 2000 Beetle in the garage.

blown 87

You are right, I am a idiot, I know nothing and have a tiny dick.

I guess it is a good thing that I have never seen a temp pressure curve graph on 134A.

dr bob

True statement. The hoses attach to the compressor via little manifold adapter plates. Two allen bolts hold each plate on, and there are two o-rings under each plate that will get replaced. At the same time, you can roll the compressor over so those holes are on the bottom, and let the old oil drain out. Put 8oz of new oil in, turn the compressor by hand a few times, then drain it out. Repeat a couple times to get as much of the old mineral oil out as you can. Add a fresh charge of oil, and turn the compressor nose-down. Rotate it a few times by hand to get the front seal wetted with new oil, and to clear the cylinders before yo upright the thing, attach the hoses, and put it in the bracket again. The little manifold adapter plates each have a charging port on the. Put a new R-134a- friendly Schraeder valve in each before you bolt them back on to the compressor housing. New o-rings in the caps, oiled and then snugged for a double seal.

blown 87

Among others that are so boring that you do not even wish to list.

dr bob

On the high discharge pressure issues on hot days, the R-134a temp/pressure chart tells all. Higher condensing temps make a much steeper pressure rise around 100 ambient than R-12. That's part of the recommendation to undercharge by 5-10% by weight compared with R-12. Another factor in a conversion decision is that the S4+ cars have better radiator fans and suffer a lot less from high condensing temps than the earlier cars. Early cars re not such great conversion candidiates. The later cars (late '93 US models onward I think) come with a better pressure safety switch, one that protects from both under- and over-pressure problems in the high side. If you do a lot of serious hot-soak slow-speed driving, updating that switch would be a good idea.

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Can't tell if I have a small dick or not anymore. I can't see it except in a mirror, and my eyesight is failing anyway. I pop a quarter of a viagra twice a day just so I don't pee on my shoes. Sucks getting old. But my converted AC is way cool over ten years later.

zoltan944

I have converted many cars to R-134 due to cost of R-12.
Ive never had a problem in Vegas on R134 even on the super cheap cars I did nothing but simply slap on the adapter and filling with a can. On cars you actually care about, you should do it right. If you have a small issue keeping R12 is a great idea. If you have to replace many of the parts of the A/C converting is a good option as you are switching alot of things out anyway. My other 928s have been R12, but the new one was switched over to R134 with the hoses, compressor, dryer, o-rings etc all switch out. The A/C is so freaking cold I can't tell the difference.
Again, R12 is no doubt instant freezing and such but if your have to switch many parts the conversion will work out great with a cheaper way to fill from here on out. Also I believe all new R134 is compatible with traces of R12 these days.
have fun with the conversion, hope you get some A/C crankin out soon

tveltman

I thought the system was charged up at the front of the engine, not down at the compressor. If I swap schraeder valves at the compressor am I Locked into 134 or is there backwards compatibility? I don't particularly care which route I go as I've never had ac in the car, so even crappy ac is better than none, and it seems like with the s4 as long as I'm careful there isn't much differnce. My goal is to get this **** running as swiftly and easily as possible. I'm still gonna have to swap all the o rings and valves, etc, so it seems like almost the same amount of work either way. However if I do all the work to overhaul, I'll be
In a position to just swap valves, flush, dry and charge for 134. It seems to me that the way to go then is to stick to r12 as long as it's not too expensive, and if the price skyrockets, my seals are ready prepped so it would just be the valves. If the seals are good, how often have you had to recharge with each refigerant?

dprantl

People hate R134A because it's way too easy to mess a conversion up and have it cool like crap because of just plain being lazy. I sometimes can't believe how some A/C systems don't blow up. I've heard of systems just vented of R12 and filled with R134A without doing anything else. Then the owner gets mad that the compressor locks up or the cooling sucks. Even the Porsche bulletin on R134A conversion is crap.

Dan
'91 928GT S/C 475hp/460lb.ft

dprantl

Yes, you normally charge the system from the low-side fitting on the charge fitting on the big pipe just under the upper radiator hose. For some reason, the Nippondenso 6E171A comes with charge ports directly on the compressor blocks. The valves on there sometimes start to leak. If it was me, I would permanently seal those things up. There is no reason to use them on a 928.

Dan
'91 928GT S/C 475hp/460lb.ft

tveltman

Any advice on how to perma-seal them?

JHowell37

If you've got a Tig welder you could weld them shut. But honestly, if you remove the compressor, when you take the blocks off, you can clean them, and install new valves. They're readily available at most parts stores. If the old ones sealed for 20 years, the new ones will probably do the same. If the protective caps are missing or damaged, it might also be a good idea to replace them as well for the added protection.

dr bob

Thomas-

There's a set of inaccessible charge ports mounted right on the compressor fittings. You won't use them, but they do need to be fixed with the right cores so they don't leak later when the new oil hits them. You'll still charge from the top/front of the car.

Landseer

On cost, I checked today at a local independent parts dealer. $8.95 per 12oz can of R12. Need to sign-up online first for a permit ( I think the charge is $25).

underdog928

I'm about ready to dive in and do the R134a conversion on my '85. My compressor locked up on the way back from SITM and my Porsche mechanic swears that R134a will work fine if done correctly. He's done the conversion many times before on older cars without a problem.

He says he will need to replace all the hoses, seals and the dryer to make sure that there are no "leftover" problems.

I'll keep you posted on the results.

By the way, we all know that R12 is an Ozone killer and R134a was supposed to be environmentally friendly. Guess what? R134a is a green-house gas! Glad our government geniuses got R12 off the market. Now you can't find anyone that will work with R12.