A ton of miss information about R134a out there. You don’t need new hoses, you don’t need a special front seal, you don’t need a new expansion valve. Flush the system including the compressor, add the correct amount of PAG or Ester oil, new orings, remove the EPR valve and run it. The PV curve is very close to R12 until you hit pressures over 200-250 PSI and I would run the charge on the low side to not hit these pressures anyway. In my dry climate I don’t worry too much about freezing up but if the factory did not have a evaporator freeze up switch one should be added. The A Bodies seem to have one. B Bodies maybe not so much.
My 68 Coronet will freeze you out with R134a.
My 72 Duster with R134a (with a retro fitted 73 Dart AC box) works poorly. I have spent a fortune trying to understand why. I recently discovered that the 73 AC box is less than a one year design. It was changed again in 74 and stayed till 75 and the end of these A bodies. I am at the point in my troubleshooting that it was in the box. Plan to install the 74+ box (evaporator) this summer. It is starting to feel like the 73 design sucks. Note it is obvious in the pressures. The low side is just too low all the time. The superheat across the evaporator is WAY WAY to high and nothing changes it. It seems like that evaporator design was just not right and I hope it is fixed in the 74+ box.
66 Valiant I just finished with factory AC system and R134a appears to be working as well as the Coronet but time tell after the first 90+ day.
These are all build from NOS seals and valves.
Jim
