Hello everyone:
My wife and I are riding around Houston in her work in progress 05 VDP. We turn on the ac and low in the windshield on both drivers and passenger side. The windshield begins to fog up on the outside of the car. Yes, you can use the windshield wipers to remove it. BUT why is it fogging up on the outside. I read all the responses. Turn down the temp and turn off the circulation button. This does work after awhile. But in 100 degree heat, this should not be happening. Could some directional flap not be working with ac on? Thanks for your help.

JDog

 

Defrost vent is open, blowing cold air up to the windshield. The humidity is condensing, just like it does on a cold drink.

As for why the defroster vent is open, I couldn't tell you if it's broken, not closing, an actuator failure... i would imagine it's a true pain in the butt to get to, though, like anything under the dash of any car.

 

Do not risk a cracked window by blowing ice cold air on to the Windshield when it is that hot outside. creates tension

 

Mine 06 VDP does the same, four condensation spots in the lower middle part of the windshield. It mostly happens when huminidity is high... and we live in South Florida! An annoying issue for sure.

 

So can this be fixed or is this something you have to live with in owning a xj8?

 

I would have thought Manual air distribution would fix it. With Auto you have no control of the vents.

 

Oh my, it seems not to be an isolated problem. I have the same issue and don't want to delve into the dash as it looks quite messy and tight in there. I just put toothpaste on and wipe off using kitchen towels around the problem area, works for a while and then redo again. A bit tedious but probably use less time time taking out the dash in a lifetime!

 

Put a dark towel across the defrost vents and set the ac to blow out the dash vents

 

Sounds like there is moisture inside the car i.e. leaking sunroof drains or moisture collecting inside the car.

This was my issue. Whenever it rained the inside windshield would get fogged up.

 

his fogs up the outside.

 

Are you sure it's not normal?
Not sure anything is wrong?
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It sounds to me to be normal. I have heard from many people that this is happening to them. I just don't know how to fix it. I guess I will get a dark towel across the defrost vents unless anyone can chime in on how to fix it. I hate to have to tear into the a/c unit to find a vent that is blocked. I wish it was a some control module that was bad and I could replace it.

 

Oh, yeah - different issue for sure...

 

Mine doesn't do that, and I live in Florida, where it's always humid and the air is always on. It sounds to me like a defroster vent actuator isn't fully closing, allowing cooled air to get to the windshield. Actually fixing that is a major job. Living with it is not.

 

Condensation will occur anytime the temperature of the collecting surface (windshield) is below the dew point. Houston is a very humid environment. I'm in Florida which is also a very humid environment and the current temperature is 82 and the dew point is 77. In theory, condensation will collect on any surface that is colder than 77 degrees. A good example of this is when you get out of your air conditioned car in the summer and the lenses on your sunglasses fog up. The lens is colder than the dew point and condensation occurs. In the winter when the collecting surface is colder than the dew point and the dew point is below freezing, frost will eventually form. This is one reason why aircraft windshields are heated. The windshield on my 2005 Super V8 is heated to prevent this as well.

 

Does anyone know if the 2005 Vanden Plas has a heated windshield?

 

The button with the F on it between the defrost button and the rear defrost button is the heated windshield.

 

The button with the F on it between the defrost button and the rear defrost button is the heated windshield.