I had vintage air in my '70 back in the late nineties and took it out because of the problem that
@TreeFarm stated. It was horrible in the winter, and during rainy summer nights. The recirculation only I believe caused the problem in summer. And adjusting the thermostat for the cycling switch to the winter setting, still didn't deliver much heat. The blower being inside was noisy compared to the factory one. My '95 has the blower under the dash in the factory unit, but is quieter than the vintage air one.
I didn't like how stiff the wiring going to the factory switch transferred movement to the terminals, but I was concerned about vibrating the switch terminals to death.
I didn't like the hose connections being hidden under the dash, inside the cab. A heater hose leak will run down under the flooring, not to mention they are difficult to access after I had sealed the plastic hose cover in place. I put insulation on the included plastic firewall panel.
I pulled it out after I got tired of no heat in a big block truck and found factory parts.
In my '90 Jimmy, I kept the factory stuff, repaired whatever it needed, then added insulation in the floor. I was using the A/C while we were on the trails at BB19 , windows down , in a black truck. It was comfortable when I saw the outside temperature up around 98*. Painting the fiberglass top silver helped some as well!
