jmayes6

1990 928 S4 A/C has Denso 10 PA 20 C compressor installed on it
that Denso Made for Porsche 1991 Model.

On the compressor it has stickers labed R134a and use ND8 oil

My 928 (I believe) was charged with R12--Has R12 High and Low fittings and
no sticker indicating it was ever converted to R134a.

I was under the car looking at the compressor with the intent of removing it, dumping the oil, and replacing it with the specificed amount (system oil charge
- 35 per cent for evaporator) as I ruptured my condensor causing a voilent
discharge resulting in an unknown quantity of oil left in the system (replaced
condensor and dryer).

I understand this compressor could have been used for either r12 or r134a, but
I assume it came with a charge of ND8 oil which is incompatible with r12 as I understand it.

Is it correct that ND8 (I think ND8 is a version of PAG 46??) is incompatible with R12?

If so, should I assume the tech who orginally put the a/c compressor on dumped the oil and replaced it with esther or mineral?

What oil would the tech have normally used if the above is the case?

I appreciate any help

jmayes6

Update for clearification--I mean Denso made it for Porsche AG--it is not an aftermarket compressor--it came from Porsche.

WallyP

The 928 was changed from R-12 to R-134a in 1993, so either the '90 or the '91 should have been charged with R-12. If your car has been converted, it has been very poorly converted, and not by a professional shop. Any legal conversion must change the fittings to R-134a fittings, and must attach a label detailing the conversion.

My guess - repeat, "guess" - is that the compressor on your car was replaced early on, and the tech didn't change the sticker. If the system has been working for some time, it is almost certain that he did change the oil from the ND8/PAG-46 to mineral (most likely) or at least to POE (possible, but doubtful).

PAG is not at all compatible with mineral oil, and not very compatible with R-12. Since there would have been mineral oil in the original system, and it is very, very difficult to remove all of the oil, I think that the compressor would have died if the PAG was left in the system.

POE is reasonably compatible with mineral oil, so it is commonly used for conversions from R-12 to R-134a, while PAG is commonly used only for new R-134a installations (totally new systems, not a conversion).

If it were my system, I would install fresh mineral oil and R-12.

The 10 PA 20 C compressor was installed starting in '89 on the GT and Club Sport, and in '90 on all 928s. The R-134a sticker indicates that it was a later compressor, probably a replacement. The spec for oil fill is 100 - 140 cc of Densoil 6. Suniso No. 5 GS is an equivalent.

jmayes6

Wally,

Thanks for the help. I think you're right. Denso said the number indicated the compressor was 1991 manufacture so it had to be a replacement although they were clear they made it for sale and service by Porsche.

Sounds like the tech when he installed the compressor, should have removed the stickers on it as he used it in an R12 application.

I had planned to remove the compressor, dump the oil in it, and replace with an approximate amount less what may be left in the evaporator(replaced the condensor and dryer). If in fact it's mineral, it should be yellowish vrs clear?????

Am I correct?

Again Wally, thanks for the help.

WallyP

I wouldn't try to use the color of the oil as an indicator of what was in there - too many variables involved. I think that the odds greatly favor mineral oil - I don't think that the system would have lived with PAG.

An earlier reference (Page 87-41) says that the oil will distribute:
Condenser - 1 ounce
Evaporator - 2 ounces
Receiver/dryer and all lines - 0.34 ounces
Compressor - 8 ounces

This was for a system that held 350 cc / 11.8 oz of oil.

jmayes6

Wally,

Thanks--if in an abundance of caution, I were to fush the evaporators (has rear a/c) which would give me a "clean system" as I've replaced the condensor and drier, I think I would have to remove them from the vehicle????

I'm not sure I could just disconnect the lines and do it in place. Any advice on flushing them?

jmayes6

Followup Note: Also it has a fuel cooler, but I assume it wouldn't need to be flushed.

WallyP

I don't think that is is possible to properly flush the evaporators without removing them, and I'm not going to disassemble the car that far withour a really, really good reason.

They hang the evaporator from the factory roof on a string and then build the car around it...

To be honest, I think that you are getting in a little too deep. If the system worked before the blow-out, it should work now with the repairs, a new receiver/dryer, a little more oil, a good evacuation and a recharge.

namasgt

Resurrecting an old thread...

What mineral oil do you guys use these days for your R-12 system?

I went to every local auto parts store close by and only O'Reilly had some mineral oil in quarts. But the brand they carry is TECH SELECT for all R-12 systems, 50 years of mobile A/C experience blah blah blah... They only had a picture of the front and it didn't say anything about viscosity. They have to order it from another local store.


Searching old threads I come up with:

Suniso No.5 GS
Texaco Capella E
Fuchs Reniso Kes

Not really finding much about Suniso 5 GS seems like there is a lot of 3GS and 4GS out there.
Texaco Capella E, I'm finding lots of old rusted vintage cans or these:

http://www.theindustriallubricantsto...ement-1-gallon

I'm assuming the old Densoil 6 is not available anymore.

So what brand have you guys been using recently that has the correct viscosity?

What is the correct viscosity? 100 mm²/s ?

And where are you buying it from?

Thanks a bunch.

namasgt

Part number 209500 is what seems to be available locally, this is the stuff I mentioned above I found at O'Reilly.

http://www.napaonline.com/Catalog/Re...Dp%3d3%26N%3d0


Here is an old thread Greg started, not sure if he actually did use them or not. R.I.P

https://rennlist.com/forums/928-foru...neral-oil.html

merchauser

BUMP

I have drained the oil in my 1989 6E171 compressor and will be keeping R12 in the system. not many threads for the correct and proper
oil to use, and where to buy. also, not clear about the proper amount of oil to use?

FredR

Paul,

With that compressor the ac system takes about 280cm3 of oil in total with some 40% in the compressor.

R12 originally uses a mineral based oil spec ND6 and it can also be lubricated with POE that was commonly used in models transitioning to R134.

dr bob

If you aren't solvent-flushing the system and replacing the drier, stick with the original mineral oil with the R12. If you -ever- anticipate converting to R134a, do it now. Solvent-flush the system, new R134a-compatible drier (all current replacements are), use POE oil. You are replacing all the o-rings and seals in the system with the green HNBR anyway. My converted system will literally freeze fingers on the steering wheel at cruise (1500-2000 RPM) in mid-90's ambient conditions. If there was a question about performance.

I think I still have a bottle or two on the mineral oil growing roots in the AC chems bin. POLAPS stocked it last time I looked. Advanced Auto? It's been a while. I have no R12 cars left here, one at my dad's in Socal. Early 1990's Volvo wagon with non-working AC. I'd rather buy him a new car than waste the money trying to get his clapped out AC back in R12 service. He doesn't drive anymore, and no AC limits the 'borrowing' the brothers inflict on it. Maybe no new car.