VX A/C issue

[wilco58]

Recently converted my 1992 Civic VX from R12 to 134a. The compressor safety valve vents pressure. My mechanic says it needs a new compressor.

The following is from a CRX forum.

I expect the reason several people have had troubles with blowing safety valves is because R-134a systems run at higher pressure then an R-12 system that the compressor and safety valve are designed for. When you run at normal pressures for R-134a your often near the safety valve pressure. Proper R-134a conversions include a high pressure cut off switch to disengage the A/C clutch when the pressure is getting too high. The high pressure cut off switch is often omitted during conversion and more often then not people get away with it. Even if only 1 out of 10 converted systems has high pressure issues that would mean a lot of them are going to blow.

I expect the over pressure issue is most common in hotter climates where the system pressures run the highest. I think the options are:
1. Install a high pressure cut off switch.
2. Run a lower charge of R-134a to try and limit system pressure.
3. Use an alternative refrigerant that runs at a lower pressure. I'm planning to run ES-12a (Enviro-safe) in my car.

I have heard that the safety valve often does not reseat well after popping so a replacement is probably required.

Any thoughts? Advice?