i am converting 1973 with R-12 to 134a. i understand you can adjust the vaule in side to alow better oreration. any know how?

ray

No, I don't. However, I do have a word of warning before making the switch. Pressure test AFTER the valve is installed. I worked at the place that did my change-over(not for the Vette) and it was still nearly impossible to get them to replace the parts ruined by a bad valve/low pressure cutoff switch.

Scot

I converted mine to 134 and did a lot of calling around to try to find out exactly what that adjustment entails. I ended up on the phone with a rebuilder up in Denton, Texas I think it was, somewhere way north of me. They informed me that the pressure adjustment was very touchy and they used a setup fixture of some sort during their rebuilding process that I could not easily duplicate at home. In short they told me not to mess with it cause if I lost position on it it would have to go back to a rebuilder to be set up. They did not set them up for 134 either. Others might though. There was a thread on CF a while back about adjusting a cycling clutch style compressor but I think that is way different from a VIR.

In the end, the only way I could determine what the best setup position was, was trial and error and I wasn't in the mood to be pulling that VIR several times with evacuating the system each time just to discover the optimal setting. I used to know where the screw was that you would adjust. Been too long ago now. I just bought the rebuilt unit slapped it on there and put in the oil and 134. Cooling was adequate. I was getting about 48 degree air. That was two years ago. It's all leaked back out now. I'm pretty frustrated with it at this point. I really don't think much of the VIR system. Apparently neither does GM.

I'm thinking of pulling the whole thing and installing a Vintage air unit maybe in a year or two.

good luck
lone73