I've scoured through the threads on A/C and on PPI and in the FAQs and there is a lot to digest...

The car I'm looking at has had all recent service and has 70K. The steering rack has been replaced; the TB/WP was done 3 years ago at about 63K Miles. Checking on motor mounts and also fuel lines.

Unfortunately the current owner stated that the AC does not blow cold at the moment. For the last few years he has recharged it as it got warmer in LA (spring) and it was fine through the summer then would go warm the following spring.

When the car was checked he was told the compressor is fine and sounds to me like a leak somewhere in the AC lines. Not sure if there is rear air (checking the car next week).

Realistically I know this is a very common problem and not an easy one. How much should I budget (and negotiate) to have the AC fixed? Is it R12 or R134? If R12 should I also have the system converted or stay with R12?

Thanks in advance,

Michael

 

R12 is banned by international conventions, however, some cars still operate on R12 as supplies are still out there but getting harder to find.
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If the car has been converted to R134A then the charging valve will be of a different size. If the change over was done correctly then all "O" rings should have been changed, plus the receiver dryer cbanged, maybe the expansion valve and the oil must be changed as well. If the "O" rings were not changed then these maybe the cause of the leak.

There are numerous threads on the change over to R134A, so do a "search" if the system has to be changed over.

If you are not sure take it to a airconditioning technicition to check. If you are a DIYer then all the change over can be done by you and the technicition can thern do the pump down, install the oil and the R134A. This will save you a lot of $s.

The TB should be changed at 4 to 5 year of service or if the miles have reached those specified by Porsche then the belt need to be changed, the tensioner overhauled and if you deem necessary the water pump as well.

As a quick check of the TB remove one of the air intake tubes and get a torch and look down the hole in top the the TB cover with a good torch and you can see the belt. Do this check while engine is idling.

With regards to budgeting costs, how long is a piece of string? If you go the the A/C technician he will give you an estimate, however, I would go to a few, especially one who knows 928's.

Tails 1990 928 S4 Auto

 

Mickster, tell us your location and the year of the car you are looking at. There might be a local who would be willing to take a look at the car and give you a better idea on what is going on with the car. On the cars with the rear A/C there are a few more spots that the A/C can leak from.

 

It's actually in Gardena, CA-LA area.

 

Tails gives good advice...

If the A/C has never been properly converted, the odds are that the O-rings are the originals. Every joint in the system is sealed by an O-ring. With age and heat they get hard and leak. Replacement is relatively simple, but you need large wrenches and access can be, ummm - interesting.

If you are a DIY type, replacing the seals will cost a few dollars, then a new receiver/dryer and recharge should take care of the problem.

You will need to decide whether to convert the system to R-134a if that has not been done. R-134a works pretty well in a 928, but most experts suggest keeping the R-12. Don't use anything except one of these two...

If you pay to have the work done, expect it to be expensive. It would be much, much better if your A/C guy has worked on the 928 before.

 

I just had my car converted to R-134. Had all o-rings replaced, receiver/dryer, and a few other pieces. My front expansion valve was already a R-134 compatible one, and I did not bother having the rear one done at this time (that might turn out to be a mistake - we'll see). I also didn't have any of the rubber hoses replaced, as some of them had already been replaced in recent years. I decided to do those on an "as needed" basis.

The old compressor was flushed and refilled with the proper oil; same with the rest of the system. Then it was charged with R-134.

Total cost was under $1k. It blows very cold air now.

Can't feel any difference to what it used to do with R-12.

 

Don't forget the "faulty heater valve" interference to proper A/C operation.

I have that problem on my '88... and my rear A/C blows ice cold whereas my front blows luke warm to cool only (depending on outside temps). Mine was already converted to R-134 by one of the P.O.s.

 

R12 is readily available and legal here in the States.
You can buy it at your local NAPA or favorite auto store. Unsure about CA though - tough rules in CA.
You must have a 609 Certificate to purchase it. You can take the simple exam on line for the certificate and it costs about $20.
R12 is about $20 to $25 a can depending where you buy it.
My advice is to stick with R12 for a system that was designed to use R12.
All the expansion valves and dryers are R134a/R12 compatible. O rings (HNBR) can also be purchased that are compatible with both. Again the O rings are available at your fav auto store. A 240 metric O ring assortment is about $25 from Autozone.

Need help finding anything - just ask.

 

Also, with respect to R134 - it is a smaller molecule than R-12, so will be more likely to leak through old hoses than R-12. And - 134 is also supposed to be phased out soon. IF you can, staying with the OE fluid in this case usually provides better performance. Wally's comments on "O" ring replacement is great counsel.

Gary Knox

 

Our cars are still R-12. That's what they were designed for and it works fine, and pressures are lower than for R134. I think the environmental issues are a wash, neither is good for the environment if it leaks or is not properly recovered. As Roger says, R12 is available and can be legally used with an EPA 609 cert, which I got.

If the car has rear A/C (and most '88's will) then the most common leak is the fitting under the pass-seat for the rear unit. Peak under the car and find the fitting-- from underneath, two side-by-side tubes go into a machined fitting and appear to disappear-- they pass through the floor-pan (with o-rings) to the control valve under the pass-seat.

If that area is oily-looking, then those fittings are leaking. (It is a low spot in the lines and leaks oil as well as freon). That can also be confirmed with a leak-tester if you want. With the system empty (no pressure) remove the fitting (single allen-head bolt), replace the o-rings and also replace the o-rings in the pair of connections towards the front in the same pipes-- when the under-seat fitting is disturbed then those will start leaking also. We haven't seen a leak anywhere else, just those fittings (two for two).

 

when you go for the fix of the AC make sure to have new hoses fitted to the compressor, the 2 compressor lines will usually be leaking at the factory crimps so replacing all of the o rings wont fix your leak
I have had good luck removing the hoses and taking them to a hose shop for new hoses and crimps

 

You can call Jeannie at (828) 766-9280, and she can prepare a complete O-ring kit that is good for both R-12 and R-134a and is correct for your particular car.

 

R12 has been banned in Canada for sometime and R134a was the replacement only available at service centres. Now there's another product available which is compatible with both systems which can be bought over the counter at my local NAPA store.

I'll have to double check what it is............haven't used it personally......yet

 

" Now there's another product available which is compatible with both systems which can be bought over the counter at my local NAPA store."

"Compatible" is sort of a loose term. It is basically impossible to find any commercial shop that will touch a system that has anything other than R-12 or R-134a (and many shops no longer have R-12 equipment). The penalties for a shop getting caught screwing up on A/C servicing can be severe.

If you knowingly take a car with a "compatible" refrigerant into a commercial shop and they contaminate their equipment, you are financially responsibe for an expensive decontamination job...

 

This is the stuff:
http://www.autorefrigerants.com/co00030.htm
Freeze R12.