Removing EPR Valves when Converting Your Mopar to 134a
This question from a 1970 Imperial owner brings up another issue common with Dodge, Plymouth, and Chrysler classic cars when converting those air conditioning systems from R12 Freon to R134a refrigerant. Here the owner is referring to our online guide to converting Mopar A/C systems to 134a.
You mention removing the EPR valve from the RV2 compressor when converting to R134a refrigerant. What is the reason for this?
All Mopars that have the original RV2 compressor use the EPR (evaporator pressure regulator) valves to prevent the evaporator from freezing, by by-passing certain internal system pressures. Because 134a systems function correctly at different pressures, and the EPR cannot be calibrated differently from the factory R12 setting, it must be removed and replaced with a thermostat. The thermostat prevents the evaporator from freezing up by temperature instead of by pressure.
For more information, download our thermostat installation instruction guide for Mopars.
We would love to hear from you if you have problems or questions about keeping your Mopar ride cool. Don’t wait until next year to fix that A/C — the record-breaking temperatures might be over, but there is plenty of hot weather left. Get a head start on cooling your vintage vehicle and you’ll be prepared for next summer’s sizzling heat.