Can I vacuum and recharge RV2 with a standard a/c manifold gauge set?

[WH23G3G]

I don't know where you post a/c questions but I'll try here. I know I'm a ways away from worrying about a/c but everything's already been replaced and on my 73 Charger. It really just needs a vacuum and charge. The whole a/c system has been replaced with new oem replacement parts. I'm using the RV2. I think I already put 8 ounces of PAG oil in the compressor but not sure if I put PAG or Ester in since I did it so long ago. I was reading the 73 chassis manual and saw the 4 gauge manifold set Chrysler used for the EPR valve pressure. Can I just use a standard a/c manifold gauge set just reading high and low pressure and vacuum? Also where do I hook them up because it's got a fitting on each hose and one on the compressor. Classic auto air told me I have to remove the epr valve and install an electric thermostat to work with r134a. I was reading the 73 Chassis manual and noticed it said 73 Darts didn't use a epr valve but the same rv2 compressor and appears to be the same setup as on a Charger. So what's the differene? Why didn't they use an epr valve? I put mine back in the new compressor I installed. Shouldn't it work because I'll be using less r134a than r12? 

[John_Kunkel]

Not sure what you mean by a "standard" manifold set, R-12 uses threaded charge fittings and R-134 uses quick-disconnect charge fittings. You could use an R-12 manifold set to charge R-134 but you'd have to improvise a way to tap the R-134 container.

Systems that don't have the EPR valve use a clutch cycling switch like Classic recommended you add to your setup. Without the EPR valve the evaporator will freeze and possibly damage it.

[WH23G3G]

Yeah I was wondering will I be able to vacuum and recharge the system with the standard R134a gauge manifold with the two gauges and 3 hoses? Since it only has two gauges and three hose connections. I remember the orginal R-12 a/c gauge manifold had I think 3 gauges one was for EPR pressure and used 4 hoses. I've read here and other Mopar sites where some owners are able to run R134a with the EPR valve and it works fine. Should I try it out since my whole system has been replaced with updated hoses, low-pressure switch, drier, evaporator, condenser, and a/c compressor?

[John_Kunkel]

I'm not a fan of R-134 conversions, some people do everything wrong and claim success with their conversion.

Even with the original R-12 system, few people used anything other than a 2-gauge manifold set to evacuate/charge the system...the extra gauge for the EPR was pretty much a dealer thing.

[Pete in NH]

Hi,

I agree with John, many times an R-134 conversion is not done properly. With R-134 you are okay with either PAG or POE (ester) based oils. POE has the advantage of being compatible with either R-12 or R-134 if you don't have a good experience with your R-134 conversion. I prefer to leave R-12 systems R-12.

You can use a standard two gauge set to charge your RV-2 system. As John said that three gauge set up was a dealer thing and I doubt many dealers had them. The suction port on an RV-2 is on the rear compressor port and the discharge or high pressure port is on the front of the compressor (pulley side). The port on the left compressor head is for the EPR test and you don't need it. In a R-134 conversion you need to put R-134 conversion fittings on you old R-12 service ports. There are two types of conversion fittings, one type you need to remove the old shrader valve cores and then thread on the new fittings. The second type threads on the old fitting and is supposed to depress the shrader valve which it sometimes doesn't do and causes all kinds of confusion.

The EPR vale was used on B and C body cars and the compressor ran all the time. A body cars cycled the compressor with an evaporator thermostat up to 1974 and then they too went to an EPR valve. The EPR valve is set for R-12 and is set for 26 to 28 pounds. To get the best out of an R-134 system you would like this to be set lower, 22 to 24 pounds. Some EPR valves are non adjustable and some have a small set screw that can be tweaked in a test fixture down to 22 to 24 pounds.