Determining proper charge

[zz28zz]

As I've posted recently, I repaired my 2000 Corvette A/C after compressor failure. Everywhere I look online says sys takes 24 oz. That includes this site, 4-seasons site, an online factory service manual, and from local Chev dealership using vin number lookup. But for some reason the sticker under the hood says 1.75 lbs. I've always heard the sticker, on the pass fender in my case, is the holy grail, but fenders can be replaced and I bought car used.


Questions;
1. How is the proper charge determined originally?
2. Is it a percentage of total system volume?
2. Does the proper charge change when replacing condenser with an aftermarket version with possibly a different volume?

TIA

[Cusser]

3. Does the proper charge change when replacing condenser with an aftermarket version with possibly a different volume?

Yes, likely.

[JohnHere]

But for some reason the sticker under the hood says 1.75 lbs. I've always heard the sticker, on the pass fender in my case, is the holy grail, but fenders can be replaced and I bought car used.

If there's any doubt, I think I would charge the system to 24 ounces and then see how it performs. If the pressures seem a bit low and/or the center vent temperatures seem elevated, then I would add 4 ounces gradually while watching the pressures.

Questions;
1. How is the proper charge determined originally?
2. Is it a percentage of total system volume?

Not having been a system designer, I can't say for sure. But I presume that Question #2 is at least a factor in the calculation, as is the oil amount.

[zz28zz]

Just as I got the A/C going again, our heat wave subsided. Now in the 80's after months of 100+ degs.. After driving around for a couple of weeks with temp sensor in center vent, seeing 41 degs while cruising down the highway and up to 50 degs in heavy traffic or stopped. A/C is always in fresh air mode and I run it in manual mode at all times. New compressor is so quiet, I can't tell if it's cycling or not. Seems to be working OK.

The only hesitation I have is knowing that the oil is carried by the refrigerant. If you're low on refrigerant then you're low on oil being supplied to compressor. So, thinking out loud, if charge is correct and there's a tiny leak somewhere, would you notice a decrease in perf before compressor becomes oil starved?