What’s an EPR valve?

It is a valve located in the rear of the v2 compressors for regulation purposes.

Check it out in the service manual. I would think the only way to know if one is there or not is to pull the hose fitting off the back of the compressor and see if it is there.

Greg

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http://www.youtube.com/hyperpack

Picture of EPR valve. https://www.ebay.com/p/1537728312
When converting to R134a it is best to remove this valve, and install a thermostic switch for clutch cycling
If you want send me a PM and I will give you my phone number. Might be easier to talk this thru.
PS: I did check, and 1974 "A" body did have an EPR valve. They were used thru 1975.

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Charrlie_S
65 Valiant 100 2dr post 170 turbo
66 Valiant Signet 225 nitrous
64 Valiant Signet
64 Valiant 4dr 170

I guess the question now is: "Do I have to remove the EPR valve?" I suppose I could take the car into an AC shop and have them evacuate the system to recover the refrigerant, then I could remove the valve, and recharge the system. The AC currently blows cold and ultimately that's the goal.

No, you don't have to remove the EPR valve, but the evap temp will not be as cold, due to the difference in pressure/temp relationship between R134a and R-12. If you do remove the EPR valve you need a method to prevent evap freeze up. That is done by adding a thermostatic switch in the compressor circuit, that senses the refrigerant temp at the evap outlet.

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Charrlie_S
65 Valiant 100 2dr post 170 turbo
66 Valiant Signet 225 nitrous
64 Valiant Signet
64 Valiant 4dr 170