The Mystery Vapor

i get it on the outside sometimes when conditions are right. wipers are not always effective.

 

Did you try using defroster?

 

That's strange. If you can

it must be on the inside glass surface. I would think defroster should take care of that. Living in cold wet climate, I need defroster almost every morning, but never had fogged up windshield not clearing for 12 miles.

 

A couple of wild possibilities:

Since you have a fairly new vehicle, it could be "gassing" of the plastic materials inside the car.
But that would likely never go away on it's own.

A leak in your heater core....meaning that part of the "moisture" really is anti-freeze.
Have you given this liquid a "sniff test" ??

The A/C evaporator will retain some water every time you turn it OFF and that gets blown toward the windshield upon re-starting.
The situation often gets MUCH worse if your condensate drain is not working right.

 

You're using the AC a lot? Running the AC, shutting down, sitting (say overnight), restarting, there can residual moisture in the system.

Try a day not using AC (yeah I know), or at the least shut off the AC at least a mile before your final destination (recall a cheesy movie with that title), and keep the fan running for that last mile, to flush out humidity. See if that makes a difference.

 

It might be the heater core based on the symptoms. If the vapor is the color of your coolant, or smells somewhat musty (hot coolant spray passing thru the core and going thru your vents sometimes smell musty) then it probably is.

But those leak only occur when the core ages so assuming it is, it would be caused by a defect. If you have a bumper to bumper warrantee and it is still good, it might be worth spending a bit to have a coolant pressure test done at the dealer. Heater core replacement is expensive due to the labor it takes to remove the entire dash to get to the unit.

Or before that you can also check to make sure the coolant hoses (in the engine bay) connecting to the core are clamped tight and not spurting coolant into the cabin. Just little things to check before spending $$.

 

It happens to me occasionally (no rhyme or reason that I can determine) and I almost never use the air conditioning...

 

Because the conditions vary. Even a plugged drain might run fine for months until sediment plugs it up one day.......and then it flows again.

Residual moisture in the A/C system will naturally rise as the evaporator heats up after the system is shut off.

IF......it happens that infrequently, WHY are you worried about it ? I mean REALLY.

 

Block him.

 

It's the TESLA's exhaust.

Have you had the A/C on?, then direct it to the screen. That should give dry air which will dry the windscreen off.

 

Is that like RAIN-X?