You should not mix R12 and R134A
R12 is also a lubricant.
When I work on R134a systems I have to add Pag oil to the systems because R134a has no lubrication properties.
At the very least, I would recover what you have in the system, put a vacuum on the system to remove all the moisture, then maybe you can try adding R134a and pag oil.
Ive never worked on my 1g eclipses a/c since I removed a while ago before I knew anything about A/C, but on any cars A/C systems, there is a high and low pressure switch, one for when the high side pressure is at a peak, the front radiator fan kicks on to cool the condensor, thus lowering the high side pressure, the low pressure switch is to kill power to the a/c compressor clutch in order to save the compressor from lack of lubrication.
I wanted to share that last paragraph with you because these switches are set up on your car for R12 and not R134a. High and Low side pressures will be differant. It may or may not work.
I actually work on medium/heavy duty truck A/C
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