Saving last half-can of refrigerant

[Cusser]

I have a 1988 B2200 truck that still has R-12. The compressor was new about 3 years ago, I did that job. Last summer, I actually had my mechanic add UV dye and weigh/add R-12, it was low (I could tell by performance and bubbles in the drier sight glass). I don't see any leaks, and have also checked with electronic detector and bubble solution, as well as the UV light/goggles thing.


Now I see some bubbles again, and a little drop in AC performance. I have cans of R-12 and service gauges, was wondering if I could add 6 oz. R-12 and then transfer the remaining R-12 from that can into a small refillable canister I've used to recover R-12 in the past. I'd pull a vacuum on that small canister, then chill it in the freezer, then attach to the remaining R-12 in the can, and let the vacuum pull most of the remaining R-12 over, rather than losing it to the atmosphere. Does this make sense? Then I could add the remainder if necessary later in the summer rather than opening a new can. We all know that just leaving the valve attached to the can will have leakage over time.

In the past I've recovered refrigerant from automotive AC systems using similar technique, but had the canister in a dry-ice bath as well. Thanks.

[DetroitAC]

Makes sense to me. The cold bottle will condense most of the R12, and what will be left in the can will be pretty tiny mass. Better put a cap on the flare fitting while it's in the freezer, or the frost will add water to the R12