No matter what mode my AC is on, the defrost vents cause fog on the outside of the windshield. I have to run wipers to keep it clear. I had AC serviced and it works, but why would this happen?

THougt there was a thread on this somewhere on the site that talked about this.

I had hope there was, but I haven't found it yet.

No matter what mode my AC is on, the defrost vents cause fog on the outside of the windshield. I have to run wipers to keep it clear. I had AC serviced and it works, but why would this happen?


It sounds like your windshield is getting so cold there, it's causing condensation on your windshield. I'm wondering why cold air is going up thru your defroster vents in the first place. I thought it couldn't do that on any A/C setting.

It sounds like your windshield is getting so cold there, it's causing condensation on your windshield. I'm wondering why cold air is going up thru your defroster vents in the first place. I thought it couldn't do that on any A/C setting.

Actually defrost is the factory default setting in case of controller or vacuum failure. It sounds like he just needs to change his vent settings. Obviously the AC is blowing some nice cold air.

Thanks too all. Yes, the air is nice and cold and my shop says the system is new and one of the best years for AC in Vettes. It is always very hot here in Florida and I like a lot of AC. But, I should be able to turn the defrost vents off and can't.???? If I put heat on, it takes the condensation off right away, but the last thing I want is heat....

[QUOTE=shesmad123;276167] But, I should be able to turn the defrost vents off and can't.???? QUOTE]

Can you change your vent settings to thru the dash?

Yes, at least it appears that all modes are working but there is still enough air to the defrost to cause the problem. Maybe a sticky valve or baffle?

No matter what mode my AC is on, the defrost vents cause fog on the outside of the windshield. I have to run wipers to keep it clear. I had AC serviced and it works, but why would this happen?

Check under the pass/side fuel rail cover. There is a vacumn valve there that may be causing a problem.

http://i51.photobucket.com/albums/f380/123Viscount/Vacuumconnection.jpg

Thank you. I will give it a look. Sounds likely since the car sat three years in an airconditioned garage. I'll bet all of my vacuum lines are dried out. Thanks again.

Thank you. I will give it a look. Sounds likely since the car sat three years in an airconditioned garage. I'll bet all of my vacuum lines are dried out. Thanks again.

Good luck with that!