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.
There are R134a replacements for the R12 models in most cases.Control algorithms, evaporator and condenser sizing, as well as a host of other factors contribute to system capacity, so simply speeding up your compressor or upgrading to a higher-capacity compressor will not necessarily increase your actual system performance.Please consider consulting an aftermarket HVAC systems company if you need help in upgrading your system. The Sanden part number is listed under "Model Number" on the label. Please contact Sanden directly if you feel you have been sold a counterfeit Sanden compressor. Please contact one of our authorized distributors to ensure that you are buying an original, high quality, Sanden compressor.