oil trapped in receiver/dryer?

[aribert]

I'm about to evacuate/recover the R12 in my '61 Ford Falcon to be able to replace the binary switch and a few other maintenance needs. I will be using an ancient (with respect to recovery machines, manual is dated '97) Flouromizer 3000H. This machine has an oil separator port, as noted in the manual but no description as to use. After evacuation, I presume to open the port on the recovery machine and use a graduated cup to measure the qty of oil separated from the R12. In theory, I should be able to determine how much new refrigerant oil to add. The compressor is good and I will be reusing the R12 from the recovery tank when I recharge the system. My question - I will be replacing the R/D. Will there be oil trapped in the desiccant - in other words more oil remaining in the R/D that will not drain out of a port? If so, how much extra oil should I consider adding? Any other guidance with respect to how much oil to add to the system? How tolerant is an R12 system with respect to a couple of extra oz of refrigerant oil? This is the first time I have opened up the system. The compressor, Sanden SD-5 (from memory) came prefilled with oil so I did not add oil to the system (again from memory, 12+ yrs ago).

[tbirdtbird]

1 fluid oz

[JohnHere]

In addition, ensure that you add only Mineral Oil, which is compatible with R-12, and not PAG Oil, which is compatible with R-134a.

Do you recall what you put in it when you last had the system apart? POE Oil perhaps? In that case, add POE Oil and not Mineral Oil.

Consider a "couple extra ounces" of oil in an R-12 system like yours to be the maximum overage of what it can tolerate.

[aribert]

Thank you both for your responses.

I was planning to buy mineral refrigerant oil. Compressor was prefilled by Sanden. To my knowledge, I did not add any oil separately (and I don't have a partial left over container of either mineral or POE as a tell tale), too long ago to remember clearly. Would I be better off putting in POE as the replacement for the oil removed from the system? My limited understanding is that POE is compatible with mineral oil but is more hydroscopic - correct?

[JohnHere]

POE (ester) Oil is reported to be compatible with both Mineral Oil and R-12. You could try contacting Sanden with the model and serial numbers of your compressor, asking whether they can tell you what the factory-fill oil was 12 years ago. Then add one ounce of the same oil into the new R/D. If Sanden doesn't know, then I think that adding one ounce of either Mineral Oil or POE should be acceptable.