I live in Miami, FL. When running the air conditioner, part of the air flow escapes through the defrost exits on the dashboard. So when it's humid outside, this problem causes the front windshield to fog up. If I put on the wipers, it clears the issue temporarily but spreads the humidity on the windshield. So, the problem gets worse when the wipers are turned off. Has anyone encountered this problem. If so, what is the solution other than my mechanic taking apart the dash to fix the issue.

 

Can't you control the vent air flow? With my cars I can use the vent buttons to enable or disable air flow from that vent.

Experiment with the buttons until you find settings that allow air to flow from the center and floor vent and less -- ideally none at all -- to the vents at the base of the windshield.

 

I too live in FL, have several cars and all of them do the same thing. Regardless of the vent settings, some of the air comes out the top and causes the windshield to fog.

 

Both of my cars have auto climate control and with the A/C set to auto and 72F the air coming from the vents under the windshield is a bit warmer than the air coming from the center vents and the "floor" vents and condensation forming on the outside of the windshield just doesn't happen.

Maybe in your case the A/C temp control needs to be adjusted a bit warmer?

A bit of a long shot but just to be safe be sure the water drains on either side of the battery are free of trash and there is nothing there to hold dampness or worse allow water to collect. If there is any dampness this could possibly exacerbate the tendency for moisture to condense at the base of the windshield.