Too cold to charge?

[Woody258]

Hello, my question and responses were deleted in the recent site hack. A few people were helping me with an issue on an 05 Corvette. I appreciate it and just a recap, Compressor and condenser were replaced due only to a bad clutch/pulley bearing and the bolt being frozen in the compressor. No a/c sticker on car but on-line info says it takes 22oz r134a and 5 oz total of pag 46.

I installed the condenser with 1 oz of oil, drained the shipping oil from the new compressor and am unable to flush the evaporator of oil. Trying to figure out how much oil to add to the compressor before install since there is probably residual in the evap.

OT replaced with old one kind of green and gross but no metal, again system was working fine, just the bad bearing issue in the pulley.

Thanks for any additional advice!

[JohnHere]

I saved a draft to finish and respond to you yesterday, but that draft also is MIA. I'll try to paraphrase what I said:

The specs that you listed match the ones I have: 22 ounces net weight of R-134a and 5 fluid ounces of PAG-46.

I believe you said that the evaporator, which wasn't replaced, is too difficult to flush. I would guess that about 1-1/2 ounces of old oil remain in it. You also said that you added 1 ounce of oil to the new condenser, but apparently none was added to the integral Receiver/Dryer, which typically retains about 1/2 ounce by itself. And you drained-out all the oil from the new compressor, so it is essentially "dry."

Taking the above into account leaves us with roughly 2-1/2 ounces to be added back into the compressor. However, none was added to the R/D, and none was accounted for that might be retained in the hard lines and hoses (usually just a trace). Therefore, I'm guessing that adding 3 ounces to the compressor will come very close to the required amount.

[Woody258]

That sounds like good advice. You are right, the dryer on mine is connected to the condenser and I did not add any additional there. 3 oz sounds good to me. I'll install that soon and get the manifold/vacuum pump from AutoZone. I'll see if I can get the whole 22oz in using a scale. If not, I'll leave a partial charge until it warms up.

Thanks for all your help. Definitely one of the most helpful and professional forums I've used!

[JohnHere]

I'll install that soon and get the manifold/vacuum pump from AutoZone. I'll see if I can get the whole 22oz in using a scale. If not, I'll leave a partial charge until it warms up.

In one of your earlier posts before it was hacked, I recall that your average daytime temperatures are now around 40-45°F, as they are in my area. That's really too cold to weigh-in a full charge unless you set the charging cylinder in warm water to raise the refrigerant's pressure or use an electric cylinder warming blanket. If not, charging it partially is a good plan. Just make sure that you write down the precise weight you put in it so that you can follow-up weighing-in the rest of the charge in the Spring.

On the rental equipment, ensure that the oil has been changed in the vacuum pump. If it's contaminated with moisture and debris from previous use, it might not pull a sufficient vacuum. And on the Manifold Gauge Set, ensure that both needles are zeroed before you begin.