Guys, I made a mistake. I added PAG oil to my R-12 system. And then I read the small print and it says for non GM systems. So it's a double whammy!

Clearly I don't want to burn out my new compressor, so I need to have the R-12 recycled then get in there and perform a complete flush.

The muffler and compressor are the areas I am unsure about flushing. Since I don't have any debris in the system, I was wondering if I could flush the muffler and compressor to remove the oil?
Rather than remove the compressor, I was thinking I could just remove the pop-off valve/drain plug then flush from the front of the car (at the accumulator orifice tube area) back?

I realize this would leave the compressor dry. But when I go to recharge, if my first can is the oil charge will I be ok?

Any and all advice in regards to a thorough flush is greatly appreciated.

Thanks much!

Lines with mufflers and compressors CANNOT be flushed with solvents. Some AC recovery machines can recover oil, and use refrigerant to flush a system in the vehicle. See pg 17 here:

http://www.denlorstools.com...g_Manual_DenLors.pdf

You'll need to find a shop that can recover R-12, and has a machine that can flush the system in the car.

I would open the lines, drain and flush out everything using compressed air. Then put 2 oz of oil directly into the compressor. I would assemble everything, install a new accumulator and evacuate to 29 in/hg. , put the remainder of Ester oil in the charging port and recharge as per gauge readings. PAG oil should only be used in new clean R-134a systems never in retro-fits.

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quote Originally posted by William Hill: I made a mistake. I added PAG oil to my R-12 system. Clearly I don't want to burn out my new compressor ...

Assuming that you have an HR6 or V5 compressor your safest ... and perhaps least costly ... option may be to bite the bullet and convert the system to R-134a now. GM/Delphi and the EPA state that residual mineral oil in an R-134a system will migrate harmlessly to the low points in the system and remain there, but I've never seen any authoritative information concerning PAG oil contamination in an R-12 system. A system flush is not required when converting to R-134a (per both GM and the EPA), just replacing the accumulator and draining the old mineral oil from the compressor.

I would also suggest calling the manufacturer of your presumably new or rebuilt compressor. They are the best source of information on their compressors, and I am sure they have encountered this problem before. If in doubt, always follow the manufacturers' instructions, if for no other reason than to comply with their warranty requirements.

There's lots more information in this recent thread. You may also find this thread a useful reference.

quote Originally posted by RWDPLZ: Lines with mufflers and compressors CANNOT be flushed with solvents. Some AC recovery machines can recover oil, and use refrigerant to flush a system in the vehicle.

As far as I know, the line with the muffer can be flushed (and dried), but the compressor cannot. GM recommends using R-12 (only) to flush an R-12 system, and R-134a (only) to flush an R-134a system. Of course, all refrigerant used to flush a system must be recovered and properly (legally) disposed.

quote Originally posted by Dennis LaGrua: [After flushing and drying] ... put [half the] oil directly into the compressor. I would assemble everything, install a new accumulator and evacuate ... , put the [remaining] oil in the charging port and recharge ...

I generally agree with this part ... except that it's easier to just add the remaining oil to the accumulator before installing it if you're going to evacuate and charge immediately afterwards. The total amount of oil should be 8 ounces, per the GM/Helm FSM ... 4 ounces added directly to the compressor and 4 ounces in the accumulator. You also need to evacuate to a deeper vacuum than 29 inches Hg (at room temperature and sea level) to remove all residual water and volatile contaminants from the system. When in doubt, RTFM.

quote ... recharge as per gauge readings.

Once again, you cannot charge an AC system properly using pressure gauge readings alone. Charging must be done by weight. The refrigerant capacity of most Fiero systems is 40 ounces of R-12 or ~32 ounces of R-134a. I do agree that, as you have previously posted, using pressure alone you may be able to get "close enough" ... but then again, maybe not. I have even charged systems "close enough" in a pinch myself without using any gauges at all. But charging by weight is the only way to be sure.

quote PAG oil should only be used in new clean R-134a systems never in retro-fits.

No! Why do you persist in posting incorrect information like this? The EPA, GM, and Delphi (ACDelco) all disagree with you. Previously posted on PFF, ACDelco TSB 05D-J-114:

"There are no Ester lubricants approved by ACDelco for retrofitting R-12 systems or for use in R134a systems." (Emphasis present in the original document.)

I do realize that some other sources recommend using Ester oil for R-12 to R-134a conversions, but I've never seen an explanation why. I think it may be that Ester oil is somewhat more compatible with any R-12 or mineral oil residual in the system. In any event, it's always best to follow carefully the recommendations of the manufacturer or rebuilder of your particular compressor, since they are who is providing the warranty. Finally, most sources advise never to mix PAG and Ester oils in the same system; apparently they are incompatible with each other.

[This message has been edited by Marvin McInnis (edited 05-13-2012).]

Sorry for the delay and thanks to everyone for their input.

I've decided to drop the compressor, (a job I'm not looking forward to) and drain it. I'm going to buy a flush gun, some Dura II flush solvent and a nice vacuum pump. I've got my eye on the Ritchie Yellow Jacket Bullet 7cfm pump. I'll flush everything I can except for the muffler line which I'll blow out with air. Then I'll replace the orifice tube, drier and button it all back up. Lastly, I'll charge it with mineral oil and R-12. I've been accumulating R-12 whenever I can when the price is right.

Then I'll change the compressor on my second Fiero because it's leaking at the shaft seal. I might blow the system lines out so I can add the correct 8 ounces of mineral oil back in.
Then I'll replace the evaporator on my wife's car which has just developed a leak.
Then I'll follow the exact process as outlined above on Fiero number 3. It's got a mineral and Ester oil mix. And probably way too much of it. When I replaced the orifice tube recently the lines were gushing out oil.

I figure with all these jobs I may as well buy the right tools. I've been researching vacuum pumps and figure it's better to get a really good one now instead of buying a crappy one twice. Not to mention the Ritchie pumps are made in the US! Who would have thunk? I've been reading about people using mineral spirits instead of the expensive flush solvents. If anyone can tell me it's absolutely safe to use I'll go with it.

Now I just need to win lotto!

If anyone thinks I'm nuts for doing or buying anything outlined above, please let me know.

Thanks Kindly!

W. Hill

[This message has been edited by William Hill (edited 05-18-2012).]

quote Originally posted by Marvin McInnis: No! Why do you persist in posting incorrect information like this? The EPA, GM, and Delphi (ACDelco) all disagree with you. Previously posted on PFF, ACDelco TSB 05D-J-114: "There are no Ester lubricants approved by ACDelco for retrofitting R-12 systems or for use in R134a systems." (Emphasis present in the original document.) I do realize that some other sources recommend using Ester oil for R-12 to R-134a conversions, but I've never seen an explanation why. I think it may be that Ester oil is somewhat more compatible with any R-12 or mineral oil residual in the system. In any event, it's always best to follow carefully the recommendations of the manufacturer or rebuilder of your particular compressor, since they are who is providing the warranty. Finally, most sources advise never to mix PAG and Ester oils in the same system; apparently they are incompatible with each other.

Good info, thanks for posting this. Although it makes me slightly concerned about the Ester oil I charged my A/c system with.

FWIW - my a/c has been working fine for about two years since I put in a rebuilt compressor, but the compressor does have a minor leak - I thought originally it was because one of the compressor mounting bolts was missing (causing the body to torque and the seal to fail) but now I wonder if the wrong oil is also a contributor.

[This message has been edited by masospaghetti (edited 05-18-2012).]

"Assuming that you have an HR6 or V5 compressor your safest ... and perhaps least costly ... option may be to bite the bullet and convert the system to R-134a now. GM/Delphi and the EPA state that residual mineral oil in an R-134a system will migrate harmlessly to the low points in the system and remain there, but I've never seen any authoritative information concerning PAG oil contamination in an R-12 system. A system flush is not required when converting to R-134a (per both GM and the EPA), just replacing the accumulator and draining the old mineral oil from the compressor."


I've had 2 GM systems converted without a flush of old oil. They simply put in the new fittings and charge (with oil). They also said the old oil would lie dormant and not be a problem. Neither gave me a problem.

quote Originally posted by William Hill: I've been reading about people using mineral spirits instead of the expensive flush solvents. If anyone can tell me it's absolutely safe to use I'll go with it.

Mineral spirits are 100% compatible with R-12 systems, but since they're not very volatile it's probably best to follow with a quick ethyl alcohol rinse and a several-hour evacuation to remove all residual solvent. I don't know about the compatibility of mineral spirits with PAG or Ester oils, though.

[This message has been edited by Marvin McInnis (edited 05-18-2012).]