98 k1500 windshield fog issues

[Cornfield creations]

Anytime the a/c is on front dash vent, or floor/dash, the windshield fogs up on the driver side. Is there a BCM that controls the doors in the duct work? Or is there something else that could be. It is so bad during the night that I can't see and the wipers don't help much.

 

[Russell]

Does the cab of your truck smell like coolant at all? Might have a heater core leak causing the truck to fog up

 

[Cornfield creations]

No. It doesn't do it with the a/c turned off with just the vent. It will only do it with the a/c on. I know the humidity is high so that is adding to it, but there shouldn't be any air seeping from the defrost vents.

 

[scrappyk5]

You will have to go under the dash and make sure the cables are closing the doors all the way. see if they are shutting all the way or is some type of obstruction. I know both my my 1978 truck and my 76 vette do not shut all the way cause the cables have stretched just enough to let a little air thru the ducts even though I have closed them.

 

[DeviousK5]

98 would have blend/mode door actuators, not cables. For sure you need to make sure there are no obstructions.

 

[Cornfield creations]

Ok, I'll have to pull it all apart and check the doors and actuators.