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Replacing Compressor Replacing Oil and Flushing Question

wrenwright on Thu June 04, 2015 9:12 PM User is offlineView users profile

Year: 1993
Make: Volvo
Model: 240
Refrigerant Type: 134a

While removing the low side fitting from my compressor, the thread locked while I was trying to unscrew it and broke the nipple on the compressor. Now I've got a ring of aluminum stuck in my hose end, but I have another hose to use and I've got another identical compressor to swap in. The Seiko compressor doesn't have a drain, and from what I've read, there isn't a reserve of oil in the compressor; it's all in the system. I did manage to get maybe a half ounce out of it though. The '93 Volvos came with r-134a from the factory.

While the system is open, I'll replace the accumulator of course and measure how much oil I get out of it. Most of the oil in the system resides in the accumulator doesn't it?

What about the evaporator and condenser? I understand that the ideal situation is to start with a system that has no oil in it. I can flush the evaporator (with some difficulty), but from what I've read on here, flushing the parallel-flow condenser is a fool's errand. If this is the case, what should I do to determine the correct amount of oil to put back in?


Edited: Thu June 04, 2015 at 9:17 PM by wrenwright

HECAT on Fri June 05, 2015 10:09 AM User is offline

When the system is shut down and evacuated; the oils will reside throughout the entire system, with much residing in the Evap and Accumulator.

Invert, rotate, and drain the compressor, which it sounds like you have done. Remove the OT and accumulator. Using the line sets (to clean them); flush the 2 heat exchangers (Condenser & Evap) separately to remove the oil. Make sure you use a proper solvent cleaner (A/C Flush), and then make sure you remove all the solvent; blow, blow, blow, and if necessary blow more. The system will then be clean, dry, and void of any oils, except for some minimal residue in the compressor. This is the only way to KNOW how much oil to put back in.

There are published oil "balancing" procedures to guestimate how much oil to put in for each item replaced. It is based on the assumption that the remaining oils are clean and at spec (remember this comes from the warranty quick fix procedure); shall we say, the educated guess. IMHO, no less a WAG, and much less applicable or effective on older systems.

Condensers can be flushed. Even metal packed condensers can be flushed. It may require specialized equipment, but it can be done. Flushing as a whole is not rocket science; but it does require some investigating, inspection, study, investment, understanding, and diligence. The true fool's errand, is to blindly try to A/C flush without such.


HECAT: You support the Forum when you consider for your a/c parts.


wrenwright on Fri June 05, 2015 6:56 PM User is offlineView users profile

Thanks for the reply, HECAT.

I've used mineral spirits followed by acetone in the past to flush condensers and evaporators in mineral oil systems, but never in a PAG oil system. I'm aware of the problems of exposing rubber and non-metal parts to acetone and only use it on metal. Is there a locally available commercial flush/solvent that I could use to flush the PAG oil out of my system or will mineral spirits/acetone work? I've always been diligent about using a lot of air to get any residual acetone out of the parts I'm flushing and have had good results in the past using this method. In this case, I'm not so concerned with getting blown up compressor bits out of the system as I am in getting the old oil out so I can replenish the oil and recharge.

Thanks again!

Edited: Fri June 05, 2015 at 9:28 PM by wrenwright

HECAT on Fri June 05, 2015 10:34 PM User is offline

The only concern I have with your method is you probably are using some type of air delivery (flushing) method, followed by the air blow; making a big solvent mist and fog cloud. All while using a chemical (acetone) which can flash like gasoline. Just make sure you are watching out for your safety and that of others.

We make the air driven "Pulsator" delivery systems and flush available from this site sponsor. Safe-Flush is very effective with much less of a flammability or health risk.


HECAT: You support the Forum when you consider for your a/c parts.


wrenwright on Fri June 05, 2015 11:08 PM User is offlineView users profile

I appreciate your concerns. I always use acetone outside and away from any source of combustion As long as the mineral oil followed by acetone will flush out the old PAG oil, I think I'll be fine.
Thanks for all the help!

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