[dentist90]

Why did R12 systems not have pressure cutoff switches? Are they not subject to the same problems of high/low pressure as 134a?

My system has had a 134 conversion, or more likely a partial conversion. The high/low side connectors have been replaced, the old oil drained out and R/D and expansion valve replaced. Whomever did it did not include a pressure cutout switch. I would like to install one before the next recharge, but 375psi for high cutoff sounds pretty high. What operating pressure ranges should one be looking for with 134a? Should the system take more or less 134 than R12, or should my mechanic just go by high/low pressures as he adds more 134?