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Model Specific Air Conditioning
1930's to 1980's Cars & Trucks
Since 1977

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Removing EPR Valves when Converting Your Mopar to 134a

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.

3 Comments
  • john reid
    Reply
    May 17, 2013

    I just changed the compressor and clutch on my 1967 plymouth..
    I left the EPR valve in the new compressor…
    Could this be why the compressor is noisy????
    Any help will be greatly appreciated..

  • lance akers
    Reply
    June 10, 2013

    i have a 1971 dodge charger with a 440 engine. How much is the thermostate switch and do i need one fore this year of a car. I dont think its got one under the dash but im not sure. And also how much oil goes in the bottom of the compresser and how much in the lines ?? I drained all the oil out and flushed the lines like you”r web site said. I took out the epr valve out of the back of the compresser also. Thanks Lance Akers

  • mike wicker
    Reply
    June 17, 2014

    i have a 1962 300g chry. it was conv to 134 when i bought the car. could not get it cold. found epr valve in comp should i remove it? i will call in morning to order what you think i need thanks mike

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