Bulvot

My 1987 928 S4 with rear A/C is blowing cool, not cold, air. I believe that it still has R12 in it. What are the recharge options? I'm looking for the quickest and easiest for now. I don't want to pull everything out if I don't have to. I do have an A/C vacuum pump, decent gauges, and lots of R134a.

• Is there an R12 compatible refrigerant that I can just add to the system?
• Is it feasible to evacuate the system and replace it with R134a without having to rebuild the compressor or do anything else requiring removal of components?

Any tips on the best way to access the fittings?

FredR

The standard mechanical equipment route to convert to R134 is to replace the existing hoses with barrier type hoses and a new drier.

The easiest way to conversion is to use POE oil that is compatible with both R12 and R134. If you wanted to use PAG oil [that is more commonly available] the system would have to be completely de-oiled to get rid of every trace of the R12 mineral oil and only then can PAG be used. I am not aware of anyone having done this but I dare say it will have been done.

Given you have the 87 I suspect it will also have the earlier seals that are not compatible with R134. The earlier seals are black whereas the R134 are [were?] green in colour. I counted some 23 seals in the system with rear a/c.

lsuwalt

R12 is still available - EBAY has plenty and I believe Roger sells it as well. If all you need is a charge, you could do it yourself.....EBAY sells the R12 charge kit/hose for less than $15.

Christopher Zach

R12 is your first and best bet. If you want to convert, you can go to POE however I have had bad experiences with that in the past (any moisture will turn to acid and can rot your condenser). PAG had a similar problem but that's been fixed with the newer double end capped oils. With DEC PAG you do want to get as much oil out as possible (flush the condenser, replace the dryer, flush the lines, drain out the compressor, flush the evaporator) but you don't need to get every last micro-drop out of the system. And replace the seals with R134 compatible ones. And fill to 80% capacity.

Really enjoying my R134a equipped 928S here. 2 years in, working fine.

808c2s

I am in the same boat as you. I believe I need a recharge of my A/C and it's R12 to the best of my knowledge. I am thinking of using R12 again, although that is not ideal for the O-Zone, but I have a place that can just recharge it with that. The cost, though, is quite higher than the R134a, $100/lb, according to my mechanic. Mind you, this is in Hawaii, where you pay for "living in Paradise" . If you want to go with the R134a, I am pretty sure you will need to make some changes to the A/C system to accommodate the refrigerant. According to my mechanic, the R134a will run somewhat hotter than the R12 at any given temperature.

Bulvot

Any thoughts on Maxi-Frig? It says that it is a direct drop in replacement for R12. No retrofit or evacuation required.

The Forgotten On

I converted my 89 S4 to R134a as well. I use double end capped PAG and had to flush everything and replace all the O rings, expansion valves, and compressor

because the compressor exploded and sent metal throughout the system under the care of a PO due to a shop doing a shoddy conversion. They didn't even flush the old oil out nor change the O rings

Anyways, the system has been working great since I did the work and has well been worth it.

But if your system is just low on refrigerant and doesn't have any major leaks I would just refill it with some R12. A $30 can will easily fill your system compared to the at least $150 in seals and parts you need to convert the system at minimum.

Bulvot

I was under the false impression that R12 wasn't available. Thanks for the correction. I will just order a couple of cans of R12.

Now....to find the low side port on the car and make sure my gauges have the right fittings...

dr bob

The low side port is below and to the rear of the jump-start terminal on the right fenderwall. It's also above and to the right of the leaks that caused the system to need more refrigerant. Adding refrigerant offers a temporary relief from the low-refrigerant level symptom. Since you'll be back regularly, treating the symptom by replacing more and more lost refrigerant, when do you think it will be a good time to fix the leaks? It's a few dozen o-rings, some hoses rebuilt, some flush solvent, some new oil, a drier, a couple expansion valves, some charge port adapters, a long afternoon of fun, and some refrigerant. Choose the correct oil for the refrigerant you want to use.

Christopher Zach

These "drop in" solutions tend not to be "great". It also makes the eventual R12 evacuation a real bear as now you have contaminated refrig. Some in the past have included things like propane (excellent refrigerant, too bad it explodes, just what you need coming out of your vents) and other odd stuff.

If your system doesn't have leaks, top it off with R12. If it does or it needs major repairs, either get the proper tools to do a R134a conversion (seals, gauge set, good vacuum pump, etc) or take it to Porsche or a certified AC mechanic for a proper refit. R134 is fine, it's just different than R12 and the tricks that make R12 go don't work in the same way for 134a.

That's just my recommendation.

Edit. Maxi-fridge and the like appear to be butane/propane. Can't seem to find their MSDS for some reason, but I really sit here and think "Hm...." when wondering if I want a propane torch in my center console. YMMV.
C

Hey_Allen

I got licensed as a HVAC Mobile refrigeration tech just so that I could legally buy and use R-12 (on my now departed MB 500SEC) after digging into the possibility of the alternative refrigerants.
The biggest nuisance with the mixed gasses is that when you leak out some, you can't measure which gas leaked, and replace that specific gas.
In the case of the mixed Butane/Propane blend, the smaller molecule will leak first, and then if you top up the system, it won't work quite as well as it did freshly charged.
You can purge the entire system and recharge it, but that ends up being time intensive and expensive if you're not doing it yourself.

Regarding the flammability, if you puncture the AC system, the oil vapor being blown out burns like a blow torch, even in non-flammable refrigerants. There was at least one video demonstrating that, but a quick just now search wasn't showing much.

dr bob

"Best" blends for cooling start out as isobutane, and have a fraction of normal propane that should be considered a contaminant. Except for the kaboom! factor.

One of our long-time contributors had a belt come loose and snag a refrigeration line. The oil in the line along with the hydrocarbon blend he was using made a nice little fire. Fortuitously, the incident was during a dyno pull, and local hands were quick to put the fire out before more damage was done.

Since any refrigerant you use will need to have the o-rings replaced and hoses rebuilt to stop the leakage... You can so easily choose R-134a, for which there are expansion valves, driers, charge ports, and future service available.

Christopher Zach

Now as a total disclaimer: I did not replace *all* the O rings and hoses. In fact the only O rings I replaced were the ones on the compressor, compressor to dryer, dryer to condenser, condenser to expansion valve, other side of expansion valve, and back again. I left the ones to the rear system alone given that the temps there are a lot lower and the vibration/stress that's down in the engine room is much less. No problems so far, will see how long I need to go before I have to add anything.

Still, just dumping in POE, switching the ports, and pulling a minimal vacuum is not going to get you a good long term solution. Nor is putting in butane/propane/whatever.

Speedtoys

There are only two options.

Top it off with R12
A full and complete R&R with 134

In between those, there is no grey area. If after 30yrs you're down a few OZ of R12, not a huge deal...really.

monkez

Oh man, this is so timely for me. My car probably hasn't had running AC for 7+ years. It holds no vacuum and it had R134 fittings *without* an R134 sticker. To be safe, I decided to change the seals in the compressor and take a peak inside. I am glad I did because I found a LOT gooey sludge. Based on everything I could read, it looks like someone may have done a half-assed R134 conversion and combined the wrong oils, thus the sludge.

So in addition to cleaning out the compressor and resealing it, I've also had hoses that to and from the compressor rebuilt, new o-rings and a new drier ready to go in. I was feeling pretty confident, but now I'm nervous all over again . You mentioned the expansion valves; do those need to be replaced? Should they be replaced or can they be cleaned?

Again, thanks to all the knowledgeable folks who help out us newbs. Its really much appreciated. Without this forum, I wouldn't have had the courage to purchase my 928.

-adam