924Board.org

Scorpio · Posted: Wed May 21, 2008 10:32 pm Post subject: Air con conversion

looking at converting my aftermarket aircon system to R134a.. will be keeping the
1)condensor
2) 944 R12 compressor

will be purchasing
1) a generic evaporator R134A
2) generic accumulator R134A

Whats needed to convert the condensor and compressor to be able to handle the R134A?
my understanding is that they just need to be flushed to remove old R12 oil
What else is needed?..do they need different seals?
_________________
1979 NA
MS1..EFI..
GARRETT T25 TURBO
BILSTEIN SHOCKS
GT BASED CUSTOM BODYKIT

Brisbane , Australia
Think mean think fast
all youll see is
my Porsches Arse!!!

ideola · Joined: 01 Oct 2004 Posts: 15550 Location: Spring Lake MI

Yes, new oil and all new seals. You might also need to consider a new expansion valve, which may or may not be integral to your aftermarket evaporator. It is integral on the stock 924 system. The expansion valves are common points of failure, blockage, leakage, etc. for any A/C system, and is one of the most critical aspects to getting proper heat exchange to occur, so you should replace it too.

It would also be a good idea to install all new barrier hoses, as the R134a molecules are smaller than R12, and are known to leak thru the old-style neoprene rubber hoses that were used back in the day (and likely to be on your aftermarket system). OTOH, it's worth noting that some here have reported that the leakage appears to be relatively minimal, so given the cost of replacing the hoses, you might be better served to just recharge the system every couple of years (unless you're really militant about environmental pollution).

While they don't provide stuff specifically for our cars, Griffiths is an excellent resource for understanding the AC systems in Porsches (and others).
_________________
erstwhile owner of just about every 924 variant ever made

Ozzie · Posted: Thu May 22, 2008 8:21 am Post subject:

IIRC all hoses have to be replaced, all seals and a flush out.
A new receiver/drier (accumulator), fill connections and maybe switches.
The evaporator should be ok.
_________________
Porsche 924 1984 (UK import) NA
Its AUTO and its BLACK
Montego Black on black/red
Engineer of Electro/Mechanical Systems Maintenance

Smoothie · Posted: Thu May 22, 2008 8:58 am Post subject:

I'm happily going along with Petrovich's post on the subject here - http://www.924board.org/viewtopic.php?t=23277 until the if/when it's proven incorrect. It just has a ring of "yeah, that makes sense". -So I'll be retrofitting my Cherokee with R134a and its' oil, a few new green o-ring seals, new receiver-drier, and reusing the olde '86 Jeeps' hoses (whatever they're made of), and reusing everything else.. (-And a system flush beforehand, and a vacuuming (30-35"hg for about 30min., right?) to "boil" out any moisture.)
The 924T is still on R12 for now.
_________________
"..it's made in Germany. You know the Germans always make good stuff."

'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox

Scorpio · Posted: Thu May 22, 2008 10:24 am Post subject:

Im guessing i could use these seals?

http://www.autohausaz.com/search/product.aspx?sid=5xfjvrernrmqnezdvuf4nw45&makeid=800019@Porsche&modelid=1263248@924%20&year=1979&cid=24@AC%20%26%20Heat%20-%20Climate%20Control&gid=6729@AC%20Conversion%20Kit
_________________
1979 NA
MS1..EFI..
GARRETT T25 TURBO
BILSTEIN SHOCKS
GT BASED CUSTOM BODYKIT

Brisbane , Australia
Think mean think fast
all youll see is
my Porsches Arse!!!

Ozzie · Posted: Thu May 22, 2008 12:12 pm Post subject:

All makes sense except that the oil used in R12 is imcompatible with R134.
Changing the seals, dryer, flush and oil is ok but the rubber hoses get impregnated with the stuff.
That is why its recommended to changed hoses.
The old oil and R134 turns acidic so for peace of mind it is safer to replace the hoses.

(I used to repair fridges)
_________________
Porsche 924 1984 (UK import) NA
Its AUTO and its BLACK
Montego Black on black/red
Engineer of Electro/Mechanical Systems Maintenance

Smoothie · Posted: Thu May 22, 2008 12:52 pm Post subject:

I've a vague recollection of reading that the oil that's included with my retrofit kit is compatible with the older R-12 oil - I'll dig that up and look at it again tomorrow. -But there are a couple of "universal PAG oil" products shown here - http://www.fjcinc.com/fjcpag.htm -at bottom with the red lables. -So I think it may be possible to do a retrofit with an R12-R134a compatible oil, and without too much component replacement.
[the "estercool" oils are apparently compatible and non-corrosive as well - http://www.fjcinc.com/fjcester.htm ]

Sanden has a very thorough-looking procedure here (incl. 2 evacuations at 29"hg for 30 min., one before removing the old oil and another after adding the PAG oil) - http://www.sanden.com/support/RETRO.html
I might take their advice, but do the "remove as much mineral oil as possible" first, then do a flush, then the first evacuation,...
_________________
"..it's made in Germany. You know the Germans always make good stuff."

'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox