Updating to r134a
If you live in WI you cannot even purchase the kits or R134a..Use the gauges and a good pressure/temperature chart to read what your system it doing is the best advice I can give.Why don't you put your gauge set on and see what the pressures are? I would think you should be able to pull the low side pretty low if the compressor is working correctly.If it cannot lower the pressure in the evaporator, it won't cool. There is NO way to know the charge once you mess with it.Now when I turn it on in this 80-90 degree weather, it isn't anywhere near 30 degrees under ambient air temperature. Has anyone bought one of the cans of refrigerant from Oreilly's or Autozone and charged their A/C that way?The Chilton's talks about this method, but it's pretty vague on the procedure.
I have included the instructions that came with my kit below.
Just pumping in new refrigerant will only give you a mix of refrigerant and air.
From what I understand, once the system is exposed to the atmosphere (e.g., when changing a compressor), you need to do a vacuum recharge in order to purge the air out of the lines.
If your E30's air conditioner has gone out (again), I highly recommend converting to the "new" refrigerant, R-134a, and replacing your compressor with a much more affordable after-market type.
Stock compressors cost about 0, rebuilding your old one will cost 0, and R-12 Freon is getting more expensive all the time.