Why is my windshield foggy & frosty?

[Adambravo]

I'm lucky enough to have a 1963 with working a/c, but, in the past month or so, I've noticed frosty mist emerging from the defroster vent unprompted (eg, right-most levers for that control a/c fan speed and temp are in the 'off' position), resulting a foggy/frosty windshield. I've tried a couple of alternatives, including firing up the defroster on HOT, and actually just turning on the a/c to get cool air coming out of the center vents.

Thoughts/suggestions on what to do next, and/or what directions to suggest to my mechanic?

Thanks in advance...

[rivgs]

There could be a plugged drain hole for the A/C evaporator or if it smells like coolant- a leaking heater core ( Horrors! )

[Adambravo]

Thanks, Kevin! Fortunately, I don't smell coolant. Where is the drain hole for the evaporator? Do I need to get the car up on a lift?

I've heard horror stories about taking the heater core out, so here's hoping that's not the problem...

[1965rivgs]

Heater core ):

[lrlforfun]

OK AB: After a 30 + year career in the used car business I have learned to live with not getting lucky with, "just something minor and inexpensive". If it looks like a duck, walks like a duck, talks like a duck, smells like a duck and feels like a duck......it's probably gonna be a duck. By the way, I really don't know what a duck smells like. This is not to say that you may luck out and not have heater core failure, it's just doubtful. Not an easy job if you do it yourself and if you farm it out not cheep so..........good luck finding someone to repair it correctly so the entire heating and a/c system works properly, which when working properly can be a very very nice thing! Mitch

[tenugent]

if you do it yourself lookinto doing it on the firewall side.i did mine from inside with seat-console-dash out &if i had to do it again i would do it from outside.im no mechanic thats just me.also when you get it out i would take it to a rad.shop and have fixed.the ones they sell are not the same size for fit.go to roa forum for instructions.good luck.t.nugent roa 12969.