A/C blowing out moisture/fog from vents

Lately I have noticed that I can see the air coming out of my vents when the A/C is on the first setting. It looks like a fog coming out of the vents. About a year ago, I had what looked like deteriorated foam blow out of the vents a couple times and then it stopped. I am thinking about doing the R-12 to R-134a conversion, and I was wondering what could be causing this problem and if I need to get a new air dryer for the a/c? TIA

foam could be one of 2 things: the ac/heater box is sealed with foam weather stripping, and the hole in the firewall where the evaporator is connected to the rest of the system is sealed with a molded foam piece. if the foam deteriorated, it would blow out the vents, as well as allow outside air into the ducting. soulds like when you have the ac on, outside air is entering the ducting, condensing due to the cold, and blowing out of the vent registers.

when you say 'the first position', do you mean "Max" or "Norm"?

Could also have some foam stuck in the drain for your condensation catch pan. Blowing into the drain tube, will dislodge the plug, but it often settles back on the drain again. I used a shop vac, duct tape and some plastic tubing, to suck the blockage out of the drain tube and the water out of the pan (after the third time it plugged up).

By the first position, I was talking about the first blowing speed setting. The fog comes out on all the a/c settings. While I have the system all vaccumed out for the R-134a conversion, do you think I need to swap out any of the a/c parts?