jmayes6

I replaced the ac condensor on my 1990 928. I confused by the shop manual.

They use the term fluid reservoir in the directions for flushing the sytem, but it is not in the system diagram. I think they are using fluid reservoir interchangably with the receiver/dyer.

I appears the shop manual calls for a flush of the sytem with r12 before the
installation of a new receiver/dyer. Then replacing the receiver dyer, evacuate
the system and fll with r12.

Is my preception correct.

jmayes6

Sorry, I mispelled fill--should be fill not fll

WallyP

It is now a violation of Federal regs to flush with R-12 - and damn expensive as well!

Yes - the receiver/dryer is the fluid reservoir for the system.

If you are just replacing the condensor, there is not an urgent need to flush the system. This only applies if you have a suitable vacuum pump that will pull a hard vacuum on the system, removing all non-condensing materials, such as air.

If the compressor fails, you really need to flush the system.

I would suggest that you replace as many of the O-ring seals at each joint in the system as is practical while the system is down.

Add 1 - 2 ounces of the proper oil to the condensor before charging the system.

dr bob

In ancient times, a 'sweep' with R12 was used to gather stray moisture, crud, and some of the non-condensible gasses (same as 'air') in the system prior to doing a full charge. The practice ir fairly obsolete now because R12 is expensive, and you can't legally discharge the gas from the 'sweep' into the atmosphere. Makes polar gopher holes in the ozone layer, a big problem because those polar gophers eat old hair spray as well as melt the ice caps.

The current practice is to use vacuum to do pretty much the same job, in conjunction with a precision fill-by-weight recharge. It doesn't clear the crud or debris out, so if you have grenaded a compressor, for instance, you need to do a solvent flush of the condenser out of the car, for example.

jmayes6

Wallp,

Thanks for the info. The proceedure seemed a little much to me for what I did. I think they wanted to
evacate the R12 they used to flush the system into a container for disposal.

Seems to me just vacuuming it down with a strong vaccuum for an extended period of time should do the trick.

Some shops just pour oil into the receiver/drier, but do you think it's better to vaccuum it in pursuant to the shop manual proceedure?

Also, I had a break in a condensor tube which caused a violent exhaustion of R12. I think the system
uses 12 ounces of oil, but I don't know how much is still in the system. How much do you think I should add?

tveltman

solvent = denatured alcohol?

borland

Before the restrictions on atmospheric ozone depleting substances like R12, it was common to drain and refill automotive R12 systems (what WSM calls flush). This was in part to remove any corrosive chemicals that typically build up in a R12 system over time. It was also meant to top off lost refrigerant. DYI would just top off the system. This is no longer done because of the high cost of R12.

If you upgrade your system with the new barrier hose, water permutation will be greatly reduced, and so will the need to do the drain and refill be cause there will be less water in the system to combine with R12 and create those corrosive compounds.

WallyP

The violent eruption will have carried some oil out with the R-12 - I'll bet you noticed that, right?

You now have an interesting problem - how much oil did you lose? Porsche says that the condensor and the receiver/dryer together will have 25% of the oil in a working system, so you know that that you need to replace at least that much.

A new compressor for the '90 comes with 3.4 - 4.7 ounces of oil, which is supposed to be the system quantity.

The minimum that I would add is 1-2 ounces, the most that I would add is 2-3 ounces. Too little oil can ruin the compressor, too much will lower the cooling efficiency.

jmayes6

Wallp,

Would you just pour the oil into the new receiver/drier? Condensor? before installation?

WallyP

Yes, before installation. Doesn't matter where - it will circulate as soon as you run the system.

jmayes6

Wallp,

One last question--The Shop Manual claims 350 cm(cubed) or 12 ounces (I assume they mean fluid
ounces) of oil in the compressor. Don't know what model they're talking about. They are also calling for 33.5 ounces of R12. But this is all new to me?

Just want to run that by you to be cautious.

Please advise.

SteveG

Generally, it is good for people to know the MY of the car. You can put that in the sig line. Not really the issue here, but it points to the need for more info. Do you have rear A/C? I believe you need 37 oz if so.

The new visitor thread is full of information and suggestions.
Welcome.

jmayes6

SteveG,

Yes, I have a rear air conditioner. Just wondering how much oil to put in after condensor tube was
ruptured caused violent escape of R12. My car is a 1990 S4.

The air conditioning capacities are in Section 87 on page 1 (87-01). It lists 12 ounces of oil in the compressor. It doesn't break it down by year as it normally does indicating this is true for all models.

But that doesn't sound right to me--so I wanted to check with the good folks on this sight.

I think what I really need to do is remove the compressor, drain out the oil via the drain plug, and
refill to 12 ounces less 2 ounces for the evaporator (have replaced the drier and condensor). I believe that is the only way to be sure. (see page 87-41 of shop manual). But I'm not sure about the 12 ounces. I may need to allow for the rear evaporator. Not sure how much oil is normally contains.

Any ideas?

WallyP

Check Page 87-129...

jmayes6

WallyP

Thanks for the input. 160 +- 20CC would be 5-6 fluid ounces assuming I converted it correctly.

I may be missing some pages from my manual as I don't find a 1990 specifications specifically.

87-129 is for MY 93 using R134 My section ends at 87 -131.

Any further thoughts appreciated.