I've currently given the car to an import mech. I will pass along your suggestion. (Normally I do my own work, but I don't have the knowledge or equipment for A/C systems.)

Would the conversion cause the compressor to be harder to turn? I'm wondering if the clutch electrical was weak to begin with, but strong enough for the original R12, has the conversion to R134a exploited this weakness?

Thanks again, I'll post when I have some results.