Haven't been on here for a while, sorry for the late reply. The factory system was shot, time had taken it's toll. Decided to replace it instead of trying to find obsolete 30+ year old vacuum parts. Plus it wasn't designed for 134A, never cooled all that well 15 years ago.
Having said that, the VintageAir doesn't cool very well either. To be clear, this is not a rant, just my experience with their system. Perhaps others considering a VintageAir system will benefit. Given the cost, the time and labor involved and the exuberant advertising, I've been pretty disappointed with it, and I wouldn't recommend their products. Being all too familiar with exuberant advertising I installed the Gen IV Magnum, the largest one they sell. It's touted as powerful enough to cool the largest sedan or wagon. Taking the usual exaggeration of performance into account, I figured it would at least cool a well insulated pickup sized area.
It doesn't. Problems aside, and I'll get to those in a minute, it simply doesn't move enough air volume to do the job. Keep in mind that with the soft top my RC is a bit smaller inside than a clubcab pickup, I never turn the fan switch below about 85%. It struggles to keep up. The cab is well insulated front to back, top to bottom, so is the soft top. Radiant heat or air leaks aren't the problem, I went to great lengths to make sure of that.
Now, the aforementioned problems. The biggest problem is that if you have a problem, VintageAir truly sucks at returning calls or answering emails. Left four messages, never got a return call, so I emailed them. Finally got a response two weeks later, and it was of no help at all. A couple months went by, emailed them again, different guy, same thing. I did notice however, the sales line answers their phone post haste. That speaks volumes to me about their priorities.
The operational issue with mine is that the ECU cycles the clutch on at 52 degrees vent temp, off at 48. Couple that with the weak air volume and it's useless if it's 90+ degrees outside, and in West Texas it's 90+ nine months of the year.
I tested and calibrated the switches, checked the resistance of the evap temp probe, tried different charge volumes, messed with it off and on for months to no avail. I then added a small microprocessor controlled programmable temp switch. It has a temp probe which I installed in one the vent hoses at the plenum. It has a relay which I use to provide a ground path for the clutch relay. In effect it bypasses ECU control of the clutch. I set the on/off parameters at 42 and 38 respectively. It now blows cold enough to do some good but has a tendency to freeze up after extended operation. The low side line from the evaporator gets covered in ice. I replaced the expansion valve thinking it might have been stuck or screwed up, same issue.
All I can come up with now is that perhaps my vacuum pump isn't strong enough to properly evacuate the system and it still has some moisture in it, or 50ish degrees is simply the best it can do with the weak air volume. Not enough volume across the evaporator to keep it thawed out at lower temps. I'm going to take it to the local A/C shop and have them evacuate and charge it, see if it helps. If not I guess I'll add an on/off switch to the auxiliary controller, turn that off and let it thaw out every so often.
Don't buy the hose kit with the crimping tool from VintageAir either. The aluminum hose ends are cheap and have a tendency to crack. Had the local A/C shop make two new hoses with steel ends in the last six months.