A/C on and the windshield gets moisture/condensation...have to use the wipers to clear it off....even when it's 90 degress outside....
A/C shop tells me the cure is to remove the entire dash, etc. and reseal the vents, etc with new caulking, foam, etc....very expensive...anyone else have this problem...cause? cure?

 

I think the more likely explanation would be the vacuum element(s) that control the defroster flap is bad. Thus the flap doesn't seal completely if at all allowing cold air to be directed to the windshield causing the condensation.

 

Something is missing here. Cold is good. What are the gaskets going to do?
Are all of your dampers working?

 

Cold air blowing out of the defrost vents on a hot windshield is not good. That's the problem.

 

No way to tell if the dampers are working....the dash I am told has to be removed and reseal the dampers, etc.
When the A/C is blowing directly at mid level and feet...the windshield still get's moisture. So something is not working! And the car is 18 years old...seals are worn out I am sure. I just thought there was a way to correct the situation without the high cost involved in removing the entire dash! I am told...the jpb will take a good 12 hours and maybe even 16. This is from 2 A/C shops who have done this before on MB's.

 

Perhaps you could rig your fresh/ outside air open partially, at least until your are ready to do the surgery. The mixed air should do the job.