If you decide to add some refrigerant, don't forget to purge the yellow (center) hose of air at the manifold gauge set. Otherwise, you'll be introducing air into the system (albeit a small amount) along with the refrigerant, which of course you don't want.

New o-rings, that is.

Looking real good. Put a shop-vac nozzle up to the ports to suck out any debris that might have gotten in there. I'd also apply a little Nylog to those o-rings just before re-assembly, and you should be all set. I hope there are no leaks anyplace else.

Of particular interest, I found the following information from Chemours (below), which is a spin-off company created from the DuPont performance chemicals business. Recently, Chemours adopted Freon™, the old DuPont trademark for R-12, to represent all of the company's HFC products, including R-134a,...

Don't forget that you can replace just the clutch assembly. You don't have to replace the entire compressor, which is probably still in good working condition.

I don't recommend introducing unknown alternative refrigerants into a system when pure R134a is readily available. As Cusser asks, why bother? Besides, you could wind up doing more harm than good. Higher operating pressures, flammability, unknown country of origin...heck, I'd just avoid using the st...

If they're not badly pitted, the joints should seal okay with a good cleaning like you did on one already, plus new o-rings. Be sure to keep any debris out of the ports and hoses. To ensure a nice tight seal, put a little Nylog Blue Label (available from this site's sponsor) on each o-ring prior to ...

You've been through a lot with this A/C already. In my humble opinion, the sound is normal for a variable displacement compressor. The compressor itself is new, the oil amount is correct, the pressures are good, it's charged with the specified amount and type of refrigerant, and vent temps are in th...

Easiest way is to drain the compressor, measure what comes out, and refill with same after repairs are completed. Otherwise, I'd figure one ounce each for the condenser and evaporator, one-half ounce for the accumulator/dryer, and maybe another one-half ounce for the lines, which of course is alread...

You also need a refrigerant scale to charge this accurately. Modern vehicles don't hold very much refrigerant and are very sensitive to the amount of charge. Just an ounce or two either way can and will cause problems. Charging with a manifold gauge set and a 30-pound cylinder is just a guessing gam...