Originally Posted by Joe H
For A/C to work the way you expect it to, the cold must blow in your face or close to it. Roof mount may not do what you want. Smaller units take less space but tend to freeze up easier. I am using the mini version from Vintage Air, in dash unit. If I don't keep on top of the temp knob, it will freeze up fairly quick. Around town, it blows super cold air, out on the road it will freeze up so I need to warm it up, then cool it back down. It works well this way, but I have been told the bigger units keep steady temps better.

Old Air Products solved this with an adjustment on the non-visible (but reachable) side of the evap box. I've used at various times all sorts of add-on units. The small units (if well-designed) will work fine. Some that claim to be well-designed, but I wonder. I had the same problem you've described many years ago when I was using a hang-down unit out of an MG and the York compressor that came with it. I was in a rush and didn't take time to check the size of the York compressor. It was too large by 2 steps. I could adjust but the thermal expansion valve just wasn't a correct match, so it would freeze up constantly. Since then I've seen some of the add-on units tend to all use the same size compressor and I've wondered about freeze-up as a result.

~ Jon
1952 1/2 ton with 1959 235 | T5 with 3.07 rear end