AC charging question

[RJRENTON]

I beg to disagree. If the EPR valve is removed, the suction pressure at the evap, can keep going down, when at low load. Then you will have evap freezeup. It is required to have some method of maintaining evap pressure above "about" 32 psi. In many of the full size Chrysler products, this was done with the EPR valve. On other Chrysler products (mostely "A" bodies) evap temp was controlled with a thermostatic clutch cycling switch. When I built the refer truck units, I used the RV-2 compressor, with a roof mounted power condenser, and a Commercial walk in cooler evap unit with a switch to a 12v fan motor. We accheived a box temp of 34 degrees, and used clutch cycling with a room air sensing T-stat.
I agree on the GM compressors. However I did have some issues with the control valve on the V-5.

Never really worked on any "A" body units...cannot speak to that end. All the B and C bodies I've worked on had pressure balanced TXV valves.....plus the only other control devices was a high pressure switch on the receiver: it also functioned thru a second contact as a NO, pressure held it closed to prevent the clutch from engaging in the event of loss of refrigerant. But I'm sure there are...... variations ....... many people remove the EPR VALVE from the RV2 COMPRESSOR when converting to R134A.....without difficulty.........
BOB RENTON

 

[Some Car Guy]

When I got my 69 GTX, the previous owner had it converted to 134 by a shop, that did exactly zero things to the car that worked right. One issue was the black o rings they left in place, another was the connector without an o ring at all.

The seller told me about the car and all he said has been found to be true. One thing is the system worked for about a year and then needed a charge, then quit altogether. Since I trusted what he said, I went through and once I found the o ring issue, I installed green ones everywhere.

I know a tech and he charged it with a snap on machine, deciding on 36 ounces. I left the epr in as I didn’t want to have nonstock parts kike a cycling switch on this car. The system worked great, but did freeze up kn max ac. I found running in normal mode it stayed cool enough in the car and didn’t freeze up.

Then the Schrader valve died. I forgot to change it. This time the tech decide to try 33 or 34 ounces. That wasn’t enough. Had air bubbles in sight glass. Ended up back at 36 ounces. I forget what the r12 amount is listed at in the fsm. I believe 36 is more like 88% of that number, quite a bit more than the amount most people say to run. It’s what my car has to have though. Maybe there are enough variances in parts that 80% is correct for some, and others need more?