A/C compressor oil. How do I know if I need more?

[EDKtrans]

OK, so a little while ago my A/C system had a bit of a moment. It was a really hot day on really hot asphalt and while idling the truck with the A/C on the system reached too high of a pressure and the over pressure relief valve opened. It vented some freon and also left a small green puddle of compressor oil, about a foot in diameter, on the ground. I have recharged the system but am wondering how to determine if I should add oil. I guess I know I should add some as some was dumped out but how do I determine just how much? Is it critical, or should I just dump some in and move on? This is a relatively new compressor and I really don't want to be replacing it.



And for those that would ask, why did it over pressure in the first place?...



The compressor was replaced a few weeks before this happened and I expect the tech put in a little too much freon. It was working but not as well as it should have. I was planning on checking the pressures when I returned from this trip I was on. Where I was idling, in Bakersfield, CA. , it was quite hot. Upper 90s to low 100s, and in the sun, on the hot asphalt it was probably well over 120. I think that at idle with the lower fan speed, the extreme heat, and the possible over filled system. that the condenser just couldn't shed enough heat to keep the system pressures in check. The fan is kicking on as it should and with the gauge hooked up it looks like things are working fine. I'll keep an eye on things but so far I think its all ok.

 

[B.G. Smith]

By blowing out that much oil entrained in the refrigerant It is possible that it had too much oil since the repair. Too much oil will inhibit the cooling capacity of the condenser and evaporator as it will coat the inside of the tubes while system is in operationn. The correct amount of oil therefore is critical. Too much causes reduced cooling, too little and compressor damage. The only way to determine how much oil is in the system would be to remove and drain all components and measure recovered oil. I doubt that you want to do that so if the pressures look ok and it is cooling normal then I would leave it as is. bg

 

[sag2]

Oil is like blood, a little goes a long way. So chances are you lost very little. But as BGS said, the only way to tell for sure is remove all parts, drain, and then add back correct amount. I would also leave it alone.

 

[Joseph Donnelly]

A few issues ago, I replaced the compressor on my 2004 and it was impossible to tell just how much oil was really in the compressor and the system. Draining the compressor gave very little oil in a cup, but I think there was more trapped inside both the old and the new ones. There is also oil lining all the parts elsewhere. If it were mine, I think I would leave it alone because you probalby have enough left in it. The instructions say to drain the compressor and then add back just the same amount that you can drain from the old one. I doubt any tech tries that because as noted above, I got very little oil from either one that way. Chances are, the system had more oil than needed after the compresor change.

 

[Wingate]

I would second that motion... do not add any extra oil

Just replaced the compressor, dryer, expansion valve on my truck due to clutch coil failing. I removed the compressor and drained, got a whopping 6-8 drops of oil... !

I decided to flush and blow everything out, put 4 ounces in the compressor and 4 in the dryer, vaccummed and charged.

 

[EDKtrans]

OK thanks guys. The system is working great since I added the Freon so I guess I'll relax and just go with it!