bshupe

1987 S4 with 45K miles - has been a garage queen before my time

I have read some strings and articles on this subject and I am ready to begin (some work done) but I thought I would ask for some advice first. The existing system apparently worked fine according to the previous owner. Evidence shows freon leaked out at some o-rings. I will replace most o-rings that I can get to. What about the following: (My 928 has rear air)

How much oil should go in the compressor? < 2 oz came out. I planned to use ester oil. Some say 4 some 6, manual much less.

I will replace the dryer.

Some say replace the expansion valves - why?

I plan to flush the condensor, what about the evaporator with rear air? Put oil in these if flushed? 1993 ed. Manual says the oil is distributed comp 40%, evap 35%, cond 15% & lines 10%. Earlier manual 1980 ed. says 75, 14, 7 & 4.

Thanks in advance, you guys are a big help. Its lonely out here in E. TN.
working on a 928...............

no doubt

http://www.nichols.nu/tip021.htm

JHowell37

Change the expansion valve, drier, and every o-ring on the system. You change the expansion valve because they tend to get blocked up with funk and ****. An A/C system uses either an expansion valve or an orifice tube. An orifice tube is considered to be a maintenance part that should be replaced whenever the system is opened. While I wouldn't necessarily change an expansion valve each time, it is a wear item, and after 20+ years changing it might not be a bad idea. In the big picture, it's not that expensive and much easier to replace when everything else is taken apart.

You can flush both evaporators and you might as well if you're going to flush the condenser. As for the oil you put in, just dump it all in the compressor. The easiest way to do it is install the compressor and leave the hose that goes from the compressor to the condenser detached from the condenser and pour in an 8 ounce bottle of the ester oil. Close it up, vacuum, charge.

Ispeed

My '87 takes 9 oz oil, and my advice: stay with R12.

dprantl

If you want the conversion to go well, you MUST:

- Change *every* o-ring in the system
- Flush both evaporators and the condenser
- Get both new expansion valves and a new receiver drier
- Make 100% sure that all the old oil has been removed from the compressor

Porsche's specification for oil in the 6E171 for a R134A conversion is 300ml +/- 20ml. Use only ester oil. Since the lines hold about 10% and it would be a PITA to flush them all, I would just stick with 280-300ml. R134A refrigerant capacity with rear-air is 1030g (36-37oz).

The only other thing in the system that will be suspect is the compressor shaft seal. Some have left it as is and have not had any problems.

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

BrettStrikes

Why go through the hassle of converting when Freeze 12 is so readily available and at such a cheap price everywhere on Ebay.....its a perfect replacement for R-12 and at a fraction of the cost of R134 even....Its worked for me for years..Even with a system with no noticeable leaks, R12 seams to vanish in small quantities. I use close to a can a year and have had a $70 supply with half left for four years.

dr bob

My 134 conversion is cold ten years later. I've added gas to it three times after the car sat for months undriven. When I drive it, the compressor seal stays lubed and it does fine. Still pulls 20º with the freeze switch jumpered, gets real cold real quick. R-12 is great but no advantage over 134 in my car. Advantage over freeze12 is that anybody can buy it. Since you need to reseal no matter what you choose, 134 is a great way to go. You can even take it to a regular shop to get service, an option not available to freeze12 users. Oh, and freeze12 is just a bit flammable so maybe not the best choice for mobile use.

YRMV, of course.

JHowell37

Isn't freeze 12 basically propane?

no doubt

Freeze Switch?

Please, do tell more.

dprantl

There is an (anti)freeze switch that plugs into the evaporator. Its function is to cut off the compressor when the evaporator temps near 32 deg F so that it doesn't freeze up. In colder climates this will cause ice to form in the evaporator that reduces or even stops air flow. If you are in a place that's very hot and jumper this switch to bypass it, the system will be able to bring the evaporator temperatures below 32 deg F.

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

BrettStrikes

I haven't looked at this post for a bit......not sure why Freeze12 gets a bad rap...maybe people don't know as much about it as one would think....non flammable and a direct replacement for R12...and is supposed to be colder since it works at lower pressures than R134...Based on the above posts...here is a link which clears things up for those that know nothing about it....based on price alone....its a certain no brainer...no shop needed for service...all do it yourself.....there are retrofit kits all over ebay which makes it profoundly simple to do it yourself....again...as stated incorrectly by Dr.Bob above....it is NONFLAMMABLE and is perfectly fine for mobile use....
http://autorefrigerants.com/co00030.htm

dr bob

Brett--

You'll want to refere to a Freeze-12 episode a few years ago where the isobutane-based Freeze-12 CAUGHT FIRE when a hose came loose during a dyno run. Quick action with several fire extinguishers saved the car.

I agree that theer are retrofit kits available, and it unlikely that one might have a fire. But last time I looked, isobutane was flammable. Especially when it sprays onto the very hot exhaust manifold conveniently placed right above the compressor. There's also the little issue of government acceptance for use in motor vehicles. Inconsequential for you I'm sure, since the refrigerant police are amazingly
understaffed right now. Still, when the effort to change is the same (fix all the leaks, evacuate and recharge...), why would you not choose to use R-134a in your S4+ 928?


Fix your post, please.

Stan.Shaw@Excell.Net

I have a much more recent 134 conversion and am happy as well. I bought the conversion kit from 928 Specialists (928gt.com) and had the work done by Automobile Associates in CT (automobileassociates.com).

BrettStrikes

Not sure if the person who said their car was damaged directly related it to Freeze12. If they did, I think they are full of sh*t. Everywhere on the net that sells Freeze12 states that it is non flammable. Not to sure where you are getting your info....another link below to help you understand...
http://reviews.ebay.com/Freeze-12-Re...T:-1:SIMILAR:1

a combination of 134a(80%) and hcfc(20%)...no propane or any other flammable substitute...and the reason I have no problems using it is that it is a cheap substitute, that works incredibly well, that I can service myself....the 4 to1 ratio of 134a to any hfcfc makes it nonflammable...........certainly possible that the oils used with any ac product may have started the fire not the Freeze12 itself....ummmm....fix your post please....*L*

Stan.Shaw@Excell.Net