Which AC Compressor Oil and How Much?

[wrxnofx]

My '87 was converted to R134 by the previous owner. It has never been charged in my 2 year ownership. This weekend we're taking it to The Hawk at Road America, and it's supposed to be 90's and 95% humidity.

My wife has requested some semblance of air conditioning for the drive, so I'm going to be charging up the AC for the first time in my ownership. Autozone just started renting out the manifold gauges and vacuum pump, so I'm going for it.

I am installing a new drier before charging the system. I realize this is all a band aid until I run through the whole system.

Questions:

1. I have no idea how much oil is in the system. When I put a vacuum on the system, does it suck out any oil in there?

2. I found an R134a Oil Spec Chart that shows Porsche's Nippondenso compressor as using an oil viscosity of 46. Is this accurate, and will this oil suffice?


3. Pending the answer to #1, how much oil do I add? When I removed the suction hose, oil seeped out of the hose itself, so I know there is oil in there. But I have seen anything from 2 oz to 6 oz. No, I am not flushing the system first.

[ganun]

6oz is total capacity, spread among the various components, ...at least you know its got oil.
Replacing the drier, just add the amount corresponding to the drier, about an oz but no more than 2.
PAG oil and 46 sounds right, IIRC.

[uwanna]

Consensus on the forum is to use Ester oil in R134 conversions, and not PAG.
Ester oil is compatible with the R12 type mineral oil left in the system when it was converted, PAG oil is NOT compatible with the mineral oil. Chances are there was a good bit of mineral oil left in your system when it was converted and the previous owner most likey used ester when he converted.
Most any R12 to R134 conversion "kit" will include ester oil for the conversion.
By the way, the vacuum pump will not suck out the oil.

[88911coupe]

So to clarify, the viscosity is a function of the compressor manufacturer, not the car type?

[ganun]

Thanks uwanna, I was thinking of a complete conversion using all new parts.

[wrxnofx]

Originally Posted by uwanna

Consensus on the forum is to use Ester oil in R134 conversions, and not PAG.
Ester oil is compatible with the R12 type mineral oil left in the system when it was converted, PAG oil is NOT compatible with the mineral oil. Chances are there was a good bit of mineral oil left in your system when it was converted and the previous owner most likey used ester when he converted.
Most any R12 to R134 conversion "kit" will include ester oil for the conversion.
By the way, the vacuum pump will not suck out the oil.

Thanks, uwanna!

[wrxnofx]

I just took off the compressor and tilted it to see if any oil came out of the suction end, and none did. So I will assume there are maybe 2 oz in all the lines, and I'll add about 4 oz to the system.

[Porsche 2]

It sounds like you are starting in the same place I started few weeks ago, and now complete with success, so far!
I removed all the hoses, the dryer, the front and rear condensers, and the Denso compressor (all original factory installed) from my 1987 911. I replaced all "o" rings and the shaft seal in the compressor. I used a 16 ounce (approx) can of auto parts store A/C flush and flushed out both condensers followed with compressed air to dry them out. I re-attached the old large hose from the evaporator and laid it on top of the frunk and out to a pan to catch the second can of flush which I used to flush the evaporator out, followed with compressed air to dry it out. (My car has had an easy life on the west coast, so is generally in very good condition). I had a local hose repair shop make up new "barrier" hoses, using the old hoses as patterns. I installed the new hoses with new "o" rings, and reinstalled the two evaporators. I also replaced the dryer with a new one. I purchased from Amazon a vacuum pump and a manifold with hoses, gauges and valves as seen all over this subject on this web site. I put 6 ounces of PAG oil in the compressor and one ounce in the drier.
Then I pulled vacuum which went down to 30 inches of mercury - the first positive indicator! pulled vacuum again for 15 minutes or so, several more times over 24 hours with no change on the gauge from the minus 30 inches mercury. Then I charged some 10 ounces of R134a refrigerant into the system with the engine and A/C system off, pressure rose to just plus 50 psi. Then with the engine at 2000 rpm and A/C system running at max positions, charged 14 more ounces of refrigerant. Vent temperature dropped from 65 (ambient) down to 40! Will now monitor system over next few weeks. My cost including taxes: hoses $375, seals and oil $20 (approx), two cans of flush solution and two 12 oz. cans of refrigerant $47, vacuum pump and manifold/hoses/gauges/valves equipment $110, new dryer $30, total $582.
Will report back in a few weeks

[Porsche 2]

I forgot to mention, that I removed the bicycle wheel tube type valves from the high and low compressor manifolds and installed R143a type quick connectors instead, thus completing conversion to R143a refrigerant. Connectors cost about $10.

[wwest]

R-134a adapter + pressure switch ports.

[wrxnofx]

Originally Posted by Porsche 2

It sounds like you are starting in the same place I started few weeks ago, and now complete with success, so far!

Good on you! At this time I am just looking to (1)see if the compressor even works and (2)give some kind of comfort for us when driving, however temporary that may be. Those black seats seem to make the cabin an oven even on a mild day.

FYI - AutoZone rents the vacuum pump and manifold gauges now!

So I added 3 or so oz of ester oil into the tube running into the suction port of the compressor, and added an oz or so into the new drier. I'm pulling a vacuum right now; we'll see if it holds and I'm able to charge it up. Fingers crossed...

[Porsche 2]

It should not take long to complete the first pull - 10 minutes?

[wrxnofx]

Originally Posted by Porsche 2

It should not take long to complete the first pull - 10 minutes?

Agreed. I just want to be sure I get all the moisture out. This thing has been open for a few days and it's crazy humid here...

[wrxnofx]

Moved post to a new thread...