Tampa 928s

80 Euro replacing compressor, Receiver Dryer and flushed the condenser.

I need the capacity of the oil that would be lost from these three parts.
Compressor 40%
Condenser 15%
R/D 10%
Total oil =?

R-12 = 950x80%= 760 grams or 1-Lb 10.8 R-134 is this correct?

Thanks

dprantl

The total amount of oil in a 928 system with a 6E171 compressor should be 280 +/- 20 cc. If you are replacing/flushing the above components and are sure there is no oil in the new compressor, then you need to add 182 +/- 13 cc.

85% of R12 charge is usually used in a conversion, so I would do 950 * .85 = 807.5g

This system has already been properly converted right? Otherwise, you should be flushing the evaporator as well to get rid of the old mineral oil.

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

jwillman

So what about pulling and rebuilding a compressor only. How much oil do you add back inot the compressor with same dryer, condenser and evaporator?

Tampa 928s

Thanks, had been converted from P.O.

dprantl

Assuming you would remove all the old oil out of the compressor during the rebuild, you would be adding back 40%, or 112 +/- 8 cc's.

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

jwillman

Thanks Dan!

Tampa 928s

New compressor "thanks for the rebuild-roger" new R/D.
Good vacuum -30 for an hour, 1.85 Lb's of R-134 drops about 30 degrees:
Pressure way too high 43/335 starts going up as it operates; seems like an open expansion valve.
When off pressure should stabilize near ambient temp seems to peg the low side for a very long time.
One line is cold but not real cold other line is very hot.
I flushed the condenser did not see any blockage, this car sat for 10-years.
Anyone want to confirm or offer any suggestions?

Erik N

Did you get your compressor rebuilt, or buy a rebuilt one?

Tampa 928s

Rebuilt by Rogers connection.

Tampa 928s

With the high pressures on both low and high and could not find any information on an open or partially open expansion valve showing a direct indication that this could be the cause.
The old compressor had very little oil in it the R/D had the most when I took it apart. I charged it up to test for leaks and from what I remember the low side was high but the high side was more like 300.

This looks like the expansion valve but the one other issue could be too much oil.

With the new compressor I opened the port cover and turned it upside down and no oil came out. I added the correct amount based on the items I replaced and flushed.

One thought is that the high pressure readings could also be caused by too much oil the cannot be compressed. Trying to get my plan together the expansion valve is being overnight shipped.

If I do have too much oil I could drain it from the compressor at the port located at the bottom. But how much is too much oil? I could be off by 2-0zs on the high side if a lot of oil is in the evaporator. But it sees that here was too little oil in the system when I took it apart.

Any thoughts?

WallyP

Pressures sound like inadequate air flow over the condenser, or trash between the condenser and radiator, or recirculating air thru condenser and radiator.

Tampa 928s

The condenser is clean, fan is on air flow seems adequate.

I measured the temp on the condenser from top to bottom:
180
156
119
118
121

Should I not see a larger drop in Temperatures?
My concern is a blockage due to it sitting and being empty for 10-years. The pressure switch on the R/D showed a rust colored coating on it that may have been from the moisture.
So both pressures are high cooling is not good where else can I look?

Landseer

Moisture saturation or excess air seem possible too

New drier? (real important)
What was used to flush the lines?
Was your shop air compressor well-filtered to remove moisture?
How did you flush the evaporator with the expansion valve in-place?



I'm still confused by oil qty. Filled mine with 350ml per WSM.

I found a chunk of old O-ring in my expansion valve. Documents show Porsche dealer worked on the system twice in the years before I got the car.

pjg

High pressure on the low side, sounds like air in the system or overcharged.

Troubleshooting tips here:
http://www.aa1car.com/library/ac98.htm

Tampa 928s

Ok here is what I have so far:
Found heater valve open, closed via zip tie, temp is now 60 degrees.
Low pressure when at 1500 Rpm close to 30

This 80 Euro has been replaced with a new style compressor with a new bracket.
I have vacuumed it down and made sure no air is in system correct R134 28.5 oz.
I added 8-Oz of oil to compressor after replacing the compressor it was dry, new receiver/dryer and flushing the condenser.

I am looking for the air blending door and do not see it, on this year where is it located, this could account for letting outside air in!

Expansion valve is on the way but after looking at all my readings that may not be the problem, thoughts?