[Stripes]

Replacing my old non working A6 compressor with a Pro6Ten on my 1974 TA. Ran into some issues. Service manual instructs to drain the (old) compressor oil, subtract recovered oil from 11 oz and reassemble with the new compressor by adding the difference into the new compressor.

I could only get an ounce of oil out of the old compressor (see photo), and it looked very dry. So the dilemma: following the service manual I would add 6 oz of oil. I'm not confident the other 5 ounces are in the system. So how much to add?

Another issue: The Pro6Ten literature indicates it comes with 6.72 oz of oil in the new compressor. When drained, only 3 ounces came out! Spinning the pulley didn't help. Has anyone else experienced this issue with the Pro6Ten?

[Squidward]

I don't have an answer for you, but just wanted to show some love.

There is no doubt that there is some residual oil in the system (VIR, evap, condenser), but like you I would question it being 5oz. In its previous life, numerous leaks/recharges probably drained much away. But wow, old compressor only had 1 oz? I'm thinking the whole system was low. It's tough to know without flushing the entire system, but sometimes you play the hand you are dealt. I would feel better to flush even just the condenser.

I would probably trust the 6.72 the compressor manufacturer was supposed to put in it, and add 3oz more after returning your compressor oil that you drained. My reasoning: There are still likely a few ounces in the system, but given that so little came out of the old compressor, I can't imagine much. So I will guess 2 remaining in the system, plus the almost 7 in your compressor, plus the 3 oz add, equals roughly 11-12. A little bit extra oil reduces cooling capacity. Too little kills compressors.

What oil and refrigerant will you be using? Assuming R12, along with compatible oil (mineral or ester)?

Saw you hanging for quite a while with no response, thought I would do my best.

[Stripes]

Appreciate the response regarding my 1974 Trans Am.
I drained then compressor oil and it looked like sludge, so I elected to pull everything and flush or replace it. Attached is a photo of the oil in the glass measuring cup. The bottle of rust oil was from flushing the condenser and evaporator. Flushed everything, installed a new Pro6ten compressor. Painted it black.
The VIR (valve in receiver) photo shows the pickup screen completely cover up with rust and sludge. I replaced it (which includes it's internal dryier), the o-rings, the hose set, and installed 6.7 oz of Ester oil. That results in 18% oil to freon ratio as the maker requests. The old A6 had a sump and held 11 oz but only had about an ounce in it. Had I not changed the VIR, I would have wasted a new compressor and a lot of time and money. I charged it with R-12 and it is cooling very well, about 43F at the vents.
The compressor vendor had no idea why the new compressor had so little oil in it from new. Claimed they had "never seen that before", however I doubt they ever checked one. It had to be drained anyway to switch to ester oil for r-12. It shows checking the oil level is critical to compressor life. Too much oil and no room for enough freon and it never cools enough.
For others like me that though throwing a new compressor on would resolve my issues, that old VIR and all that rust would have never run right. This system was closed and had freon in it when I began this project, but not cooling. There is no fast way to have reliable AC without doing it all.

[Squidward]

Way to go, you did it right!

I would've thought the compressor manufacturer would have a little better quality control on the oil amount.

I didn't know how serviceable the VIR's were, and it seems the only replacements I ever saw were the VIR eliminator kits. That was some nasty stuff!

I love how the old systems work, they blow some ice cubes. The CCOT systems are simpler with cheaper/less complex parts, but they can't rival the POA/VIR stuff for pure frostiness.

[Goatracer1]

I believe it was in the service manual that I saw how much oil is retained in each component. If not it should be online some place.