ac replacement

[chvytys]

Need to know how much oil to add to the new AC compressor.....

[BNaylor]

Welcome to AF.

It would help to post what model and engine you have. Wasn't the new compressor filled with oil? Did you drain it?

The total A/C system requires around 8 ounces of PAG 150 oil. A typical Delco/Harrison V5 compressor requires 3 ounces.

[rkvons]

Originally Posted by chvytys

Need to know how much oil to add to the new AC compressor.....

This is a good question. Like BNayler said, it requires around 8 ounces. Hmm, but how much is in the system? If you assume that the proper amount of oil was in the system before you removed the old compressor, then you simply drain the oil from the removed compressor, measure it and then put that much in the new compressor. But was the system intact? Sometimes a leak in the system will leak oil. Now you don't know how much is in the system, so you don't know how much to add. You then have to flush and start over. I recently replaced a compressor and followed the directions to the letter. They said to pour out the oil in the removed compressor and replace that exact amount in the new compressor and then put it back together and charge the system. Well, what those directions failed to take into consideration is the fact that my compressor was leaking oil and that was why I was replacing it. After I put it together, it got incredibly cold, but the compressor went out in less than year. After the second time around, I again was not sure how much to put in, so I kinda guessed. After driving it on the expressway, I would notice that it would freeze up and stop cooling. So I went out and bought an oil charge kit (about 2 oz.) and put that in. It seems to be okay now. If there is too much oil in the system, it won't get cold enough, but will last forever. If there is not enough oil in the system, it'll get cold enough, but just won't last.

So here's a question: how do you flush the system to start over?

[BNaylor]

Originally Posted by rkvons

This is a good question. Like BNayler said, it requires around 8 ounces. Hmm, but how much is in the system?

You either misunderstood me or misquoted me. The complete A/C system needs 8 ounces of PAG 150 oil. The compressor itself is 3 ounces.

Also, the instructions you see about compressors and the PAG 150 oil take into consideration the compete system has been properly evacuated of all refrigerant and oil and that you are starting from scratch.

BTW - IMO the only time you have to flush the system is if you note metal shavings or excessive debris at the orifice or see any when removing the compressor suction and discharge lines. If there are no metal shavings then after everything is put back together then the next step is to pull vacuum to get all the moisture and foreign gases out like air before adding the requisite remaining PAG oil and the proper amount of R134a refrigerant. Vacuum to 28-29 inches or at least 500 microns with a vacuum pump.

[rkvons]

Sorry about the mis-representation of what you said. I still wonder, though, how you can ensure that you have the right amount of oil in the system since it is distributed throughout instead of being just in the compressor, without flushing and starting over.

[BNaylor]

Originally Posted by rkvons

Sorry about the mis-representation of what you said. I still wonder, though, how you can ensure that you have the right amount of oil in the system since it is distributed throughout instead of being just in the compressor, without flushing and starting over.

I see what you are saying and getting at but I don't see where the subject of flushing is relevant to the OP's post unless we know what the circumstances are and from what I can see we don't. All he asked about was compressor oil content.

As to flushing I agree at times it may be necessary but it depends on the circumstances. Refrigerant contamination, contaminated PAG oil, dessicant bag failure in the accumulator, too much PAG oil, etc. Just because you replace a compressor doesn't mean you have to flush the system. Not all compressor failures are the shaft seal or the o-rings meaning a leak and/or a significant loss of oil for that matter. Whenever a compressor is replaced the orifice should be cleaned or replaced and the accumulator replaced and resupplied with oil. One reason is you are supposed to drain and measure oil in the accumulator. If the oil drained is greater than 3.5-4 ounces then technically a flush should be performed to get rid of the excess oil. If less than the above then all you have to do is add the difference missing into the accumulator direct.

If you are really concerned with whether you have too much oil then it is best to take it to an A/C shop where they have the proper evacuation, recovery and recycle equipment. For example GM dealers use the ACR 2000 Air Conditioning Service Center which does it all including flushing and vacuum. Even with the fancy flushing equipment you have to manually drain any oil out of the compressor. The flushing process does not flush the oil out of the compressor. That means removing the compressor to do it and even the orifice tube for one of the steps.