Hey everyone. I'd like to get my AC working properly again. At the moment, it's just wimpy, and the drier isn't frosting up like it used to.

I'm pretty sure it's low on refrigerant, it DOES cycle, but only gets cold when I run the car hard. Engine rpm doesn't seem to matter, but accelerating fast or changing the engine rpm quickly does matter.

Anyway, assuming it's low on refrigerant, I plan to top it off with autofrost, not do a whole retrofit. A lot of R-134a can-taps have pressure gauges on them.
I'm not going to buy a $100 manifold gauge set, so I'm looking for a cheap way to check the pressure. If it came to it, I would do a whole autofrost/R406a conversion, not the R134 conversion.

Here's what I'm thinking:
1) Find a cheap R12 can tap that measures the pressure.
2) Buy the R12-R134 fitting adapters and hook up an R-134a can tap (with a gauge). The adapter and gauge-tap would be something like $25 at walmart.

With option 2 - would the pressure be right? Pressure is pressure, right? Also, could I tap any can with it? If I get a side tap, I assume I could.

Happy Bricking,
Will
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1990 740 Turbo, on its way to stock specs, maybe beyond