Hello all, I am currently working on my Pontiac's air conditioning system, and have run into a bit of an imp***e due to lack of any clear information. My car came equipped with a GM/Harrison/Frigidaire A6 style compressor and dis***embling and inspecting the compressor cartridge , I found it was in excellent shape with just a little bit spot rust after sitting for 30 years. I decided that I was going to re-seal the unit for use with R134a (I am converting the system to R134a, all the R12 leaked out decades ago). However, the unit is still soaked in the original mineral oil, and I know that mineral oil is not R134a compatible at all. However, I have also heard not to flush or clean compressors, but the unit is so large that a considerable amount oil within is trapped within the compressor cartridge. So I was wondering what's the best way to deal with the mineral oil? Is it safe to use AC system flush-solvent to rinse the unit? Is it okay to leave that amount of mineral oil within an R134a system? Anyone have any good ideas?
I don't know what tools/equipment you have available to you or your level of skill or comprehension...but you ask the question. Mineral oil is not miscible with R134A. Short answer you need to remove all the mineral oil you can. PAG is what was selected to be used with R134A for lubrication and I'm going to add...in a new system. PAG and mineral oil do not play well together so....in a conversion POE poly oil ester or 'ester oil' and mineral oil in miniscule amounts, do get along and it is a choice for R134A applications in conversions. The way the compressor is lubricated, is with the oil in the refrigerant....otherwise the refrigerant is a very good solvent. I would be reluctant to use a automotive store flush... If I was doing this job, I would verify the system is flat...out of refrigerant. If isn't, whatever is in there needs to be recovered, not vented to atmosphere. Then I would purge of atmosphere and pressurize the entire system with dry nitrogen at a minimum of 120 psig to perform a leak check. Use water and Dawn dish soap in a trigger squirt bottle, soap all your joints and hoses...old hoses will leak. Repair/replace all the leaks and continue to repeat pressure tests. There should be NO pressure drop over 24 hours....I would do all this to make sure there wasn't something like a failed component in the system that couldn't be repaired....you very well may find that the compressor seal is dried out and cannot be repaired. Then pressure purge the system with dry nitrogen, filling it and releasing it to atmosphere...catching the entrained oil as the system depressurizes. I'd probably pressurize the system thru the low (suction) and release thru the high side (head) or even remove a line on the high side and blow thru the low side and repeat. Then blow thru the system the opposite way....re***emble with a new liquid line filter/drier and re-pressure test. Your POE can be introduced into the system as you start to pull the vacuum Then evacuate less than 500 microns and break the vacuum with dry nitrogen and re-evacuate. Then weigh in your new charge and I'd start with about 80% of the original nameplate charge. Operate and trim charge based on performance....easier to put some in than legally get it out. But then again, this is how I'd do it for me or for hire. Yes, work at getting as much mineral oil out as you can Use POE in a conversion Disclaimer: Your outcome may be different based on attention paid to detail, hygiene, along with the condition of the original components. It is illegal to intentionally vent refrigerant to the atmosphere...which is what you will do if you don't identify and repair the leaks. Two of my Hot Rods are Roadsters and the cooling works well in the winter and the heating in the summer. The other one is enclosed but it is banger powered so I'd rather go fast to be 'cool' than to be cool and go slow... it doesn't have air conditioning either..... Good luck
Thanks for your reply, I'd like to think I understand the basics of refrigeration systems, but I'm no expert. The system has been LONG flat of R12, probably since before I was born. The car was stowed away in '86 and I got ahold of it in '17. The system is largely apart and I am replacing much of it, the only remaining components being the evaporator and the compressor. I'm replacing all of the lines with barrier hose, the condenser with a new parallel flow unit, a new TXV, and rebuilding the Suction Throttling valve. I actually have the compressor taken apart to its piston ***embly (the A6 is pretty easy to dis***emble) to replace the internal seals with new R134a compatible seals. GM offers a PAG lubricant for use with these compressors as well, which I was planning on using (AC Delco PN 15-118, 150 Viscosity oil). I was wondering if any solvent would be safe to use in this situation to clean the compressor internals of the mineral oil. I have seen multiple answers ranging from acetone to denatured alcohol to standard AC system flush you find at parts stores.
You probably know more about the A6 compressor than me but I tried to use one on a 134A system and the seal leaked after a couple years. From what I read at the time, those seals barely held the R-12 freon and did not do well with the 134A. On a new system like what you have, I would pick up a Sanden compressor.
Well, I already have the seal kit on the way. This compressor is in pretty good shape mechanically, so I'd feel bad ditching it for a new unit. With new 134a compatible seals I imagine it has plenty of life left in it.
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