AC compressor flushing: Mineral oil -> PAG.

[SilberUrS6]

Having searched and having found some contradictory answers, I will ask a question.

Background: Changing out front condenser, evaporator and hoses. Keeping rear condenser and Nippondenso compressor. Switching from R12 to R134a. Have can of PAG oil in hand.

OK, so I know that PAG and mineral oil are not compatible, and I will need to get the old oil out of the rear condenser and compressor. Can my AC guy do this with some solvent and the parts out the car?

On a tangentially related question - I'd like to get a high/low pressure switch to cut of the compressor if the pressure is too high or too low. Any suggestions on which one and how to wire it up?

Thanks, guys.

[jmohn]

Easiest solution is to use ester (POE) oil not PAG. I would not suggest using PAG (at all) in a system that had previously used R-12.

Jerry M
'78 SC

[kuehl]

You could use a variety of dedicated liquid flush solvents available through most
auto parts brick and mortars.

For the deck lid condenser you could flush it in or out of the car, in the car takes
less time but doable with a simple drain hose to a can.

For the compressor, although the amount of old oil in it is little to none, best to remove the compressor, flip it over a large clean coffee can, turn outer hub several times in each direction and tilt compressor to help drain what ever is in it, and inspect the residual oil for signs of contamination to determine if you should go further.

POE is 'ester' in case you are trying to locate it. And, Ester conversions are easier than PAG conversions. Can mix ester with mineral, but you can't mix ester with PAG or PAG with mineral.

We prefer to install the low high pressure switch in the new barrier hose, compressor to deck lid condenser, HERE

[SilberUrS6]

Originally Posted by kuehl

You could use a variety of dedicated liquid flush solvents available through most
auto parts brick and mortars.

For the deck lid condenser you could flush it in or out of the car, in the car takes
less time but doable with a simple drain hose to a can.

For the compressor, although the amount of old oil in it is little to none, best to remove the compressor, flip it over a large clean coffee can, turn outer hub several times in each direction and tilt compressor to help drain what ever is in it, and inspect the residual oil for signs of contamination to determine if you should go further.

POE is 'ester' in case you are trying to locate it. And, Ester conversions are easier than PAG conversions. Can mix ester with mineral, but you can't mix ester with PAG or PAG with mineral.

We prefer to install the low high pressure switch in the new barrier hose, compressor to deck lid condenser, HERE

Well, as it turns out, I got a hi/low switch with my kit. So, no worries there. I did, however, select PAG rather than ester oil when I ordered. I'm guessing that if I call and ask to exchange, and have not yet opened the can of PAG, that you will take back the PAG and send me ester? I hope so, but I'm sure I can pop for a whole 'nother kind of oil.

Thanks for the info, and I think I will take both the condenser and the compressor out of the car to get them cleaned up.

[huba]

JerryM, Noticed you have a 78 911. What's the chance you have A/C in yours? I have a 78 911 with factory or dealer A/C (I don't know for sure which) and the hoses under the hood ---back of dash are pretty much discombobered. I really would like a picture of how it all fits together. Thanks, Huba

[jmohn]

Originally Posted by huba

JerryM, Noticed you have a 78 911. What's the chance you have A/C in yours? I have a 78 911 with factory or dealer A/C (I don't know for sure which) and the hoses under the hood ---back of dash are pretty much discombobered. I really would like a picture of how it all fits together. Thanks, Huba

Huba

Yes my '78 has A/C (currently in need of re-charge), aftermarket, manufacturer was "CCCCool". I'll take some pic's and post soonest (2-3 days).

I suggest starting a new thread asking for info on '78 A/C systems, I'm sure you'll get other responses and this may help you determine if yours is factory or not (valuable info) and I'll try to post pic's to that thread.

There is also (IIRC) a tech. write up here on Pelcian that discusses early Porsches' air-conditioning sytems.

Jerry M
'78

[kuehl]

Originally Posted by jmohn

Huba

Yes my '78 has A/C (currently in need of re-charge), aftermarket, manufacturer was "CCCCool". I'll take some pic's and post soonest (2-3 days).

I suggest starting a new thread asking for info on '78 A/C systems, I'm sure you'll get other responses and this may help you determine if yours is factory or not (valuable info) and I'll try to post pic's to that thread.

There is also (IIRC) a tech. write up here on Pelcian that discusses early Porsches' air-conditioning sytems.

Jerry M
'78

Briefly: "Factory" air in 78 onward was made by Behr, you'll find their logo on the top of evaporator box under the smuggler's box cover in the front trunk. Hoses routings are slightly different for the CCCCool system at the evaporator and TEV, and depending upon whether they used a front condenser and which deck lid condenser they used you might have differences compared to a Behr system.

[huba]

IIRC is aperson? Do I just contact him on this web site? Huba

[huba]

By the way, I took the York comp and bracket off temporarily until I decide whether to replace with a newer design?

[Targalid]

Huba,
This is a question I can answer! IIRC: If I Recall Correctly.

[huba]

O.K. So now I really feel bright. Thanks.

[88911coupe]

Just curious, what is the reason that PAG and mineral oil can't be mixed?