Replaced just about everything Ac won't work

Wow, I'm frustrated!
I have a 72 Scamp with a slant. It's an ugly 4 door driver, but it HAS to have working ac. When I got it, some of the factory ac parts were missing and some were replaced with aftermarket and hose clamps, etc..it was a mess.

I chased down all the correct hoses to and from the compressor, got a good used factory condensor, put in a new dryer and put it all back together. I upgraded to the new green O rings. I even replaced the dash vacuum switch because I wasn't getting power to the compressor (even with the pressure switch shorted out of the circuit). (The dash switch fixed the problem with power to the compressor)

This is the second time I've charged it with the same result. I pull a vacuum for an hour, let it sit and there's no leaks. I charge it with an R-12 drop in. (NOTE: At this point I don't have the patience for a lengthy discussion on the perils of flammable hydrocarbons vs 134, etc. The problem I'm having would most likely come with any refrigerant) I seriously doubt it's a charging or overcharging problem.

After 1 can, the compressor kicks on and sound's good (no knocks or rattling). The high pressure goes away almost to zero, and the low side stays between 25-50.(Before anyone asks, I DO have the hose hooked up correctly, gas comes out if you disconnect it from the gauge set. I've had people say "it CAN'T be on zero"..it is. It goes up slightly if you turn the compressor off.)

It acts like a restriction in the line.

I thought it was the expansion valve. I just put a new one in. I pulled all the hoses and individually each checked for blockages. You can blow through all of them. The same is true of the condensor. I put it back together, charged it and it was the same.


The only thing I have found is that the evaporator in the heater box seems to be a little restrictive (as determined by blowing air through the holes with all the hoses (and evaporator valve) disconnected. You can blow through it but it requires some effort. I have two heater/ac boxes from parts cars here and they seem to flow better than the one in the car.

This is one of those situations where if you change enough parts, it will all be new and will pretty much have to work!

I'm down to two options (there's only two original AC parts left on the car!) #1. Replace the heater box and evaporator. It's a pain and I'd rather not if I don't have to. Is the reduced flow there a potential cause of my problem?

#2. I could replace the compressor. The one I have runs well and doesn't make noise. I was always told that's how you determine if it's good. Is it possible that the reed valve or something internal could keep it from making pressure? (Again, respecfully, I'm not interested in discussions about converting to newer parts, etc. I can get the compressor it came with new and bolt it on in a hour. I'd do it in a minute if I thought it would fix the problem. It would SUCK to replace it and still have what I've got now!

I would really appreciate any constructive suggestions from anyone who may have had a similiar problem!

Thanks in advance!