Chry EPR system

[Cornbinder89]

Ok, I am going to "date" myself with this, but I am old enough to remember and have worked on Chry corp cars with the RV-2 compressor and evaportator pressure regulator.
They were the only mfg to use this system and didn't use it on the cheapest (Dart) models with AC.
It is basically a commercial two temp pressure regulator that is in the suction line of the compressor. There is no frost switch in the evaporator, the evaporator pressure and therefor temp is held at a constant setting that is just above frost temp. It works like a CCOT system, in that the evaporator temp is held at a level by suction pressure.
SO, the A/C clutch stays engaged when ever A/C is called for the evap only "sees" a low side around 28-29 psi. A Tx valve was used for high side metering.
As I remember, it worked fairly well and was trouble free. It had the benefit of the clutch always staying on when A/C was called for, so no cycling regardless of load.
Does anyone know why they were the only one to use it and why it fell from favor? Was it a problem, and my experience of trouble free was an anomaly ?

[CJB]

I don't have the answer for this, but, I assume it was, as it is today, for competitive reasons. It seems every overly complicated a/c system of the past was that way so the manufacturer could boast a better or more responsive system. One thing I know for sure. I don't mind too much the way things are today. A/C systems are still one of the few areas where things have remained just complicated enough.

P.S. Thanks for being the first to post in the new forum, which gives me a chance to see how things are working.

[Tom Greenleaf]

I'll try a pic of one of these.........
> here if it shows > (it didn't)
^^^^ Was there may not post or last?

These were the first ones I noticed when anyone bothered to have A/C at all which was a VERY costly option. Was like what I still call a "lawnmower engine" and problem was it also sounded like one! Was also as tough as a good one.

Stem valves used (not Schraders) on two I dealt with intention was so you could remove this and not lose the refrigerant charge of the rest of the system if only to move it out of your way.

None failed in normal life of any vehicles I knew of with these till they were classic vehicle to antique. TMK this thing is almost exactly a flat head engine.

Cornbinder89 - I'm almost sure this could be had for the Dart and definitely the Coronet mid 60s into the early 70s.

The same found it's way into Ford products as well and others. Near sure I knew of a guy with an F-250 pickup truck cut off lines as he wanted it as an air compressor more than having A/C in the thing could fill tires and run air tools.

Will work on getting used to the format and get a location for a sign off locked somewhere,

[Cornbinder89]

The Dart could have A/C but they didn't put the EPR valve in the compressor on the Dart model, it used a conventional frost switch in the evaporator. You could tell by the suction hose fitting on the back of the compressor, the ones with EPR had a bigger (longer/deeper) fitting and an "extra" service port on the hose fitting.
None of the Chry stuff I worked on had the backseat service valves, Some of the Ford and AMC with the 2 cyl recips did.
My Marmon Semi was the last vehicle I have seen to come with back-seat service valves, It was a 1992. I once change a failing compressor in a parking lot with no A/C tools, just wrenches. Shut the backseat valves, pulled the compressor and clutch, installed the new one, and purged the compressor by cracking the suction with the high side loose, then tightened and opened the valves, I put them on the APU (aux power unit) I built for my trucks, you can still get them.
If you have room, I think they are worth it, but most times there isn't room to fit them.

[Cornbinder89]

Did some technical reading on industrial two temp valves, basically the same thing as the Chry EPR , and found they control the temp better than a thermostatic switch, I'm guess Chry placed it inside the compressor to minimize the section that could see low pressure or even vacuum, which might allow ingress of air if there were fittings and hose between the valve and compressor, Good system but more expensive than a frost switch.