2nd Gen Non-Engine/Transmission heater

[lumberjack98]

new to diesel trucks. mine is warm and usually performs ok (temp @ 5/8 fan on 2 and vents on feet) but when driving and the temp goes from above 42 deg to below 38 deg the windows will fog up sometimes i have to open the windows and even pull over and wait till clear. (truck interior dry) any sugestions about what it could be (I've cleaned the heater box) wrong setting? Thanks

 

[ata]

Sounds like your heater core is starting to leak.

 

[lumberjack98]

leak

I havent had to add any coolant even to the bottle.

 

[Matt42]

Leak

I havent had to add any coolant even to the bottle.

It doesn't take much of a heater core leak to produce the symptoms you described. A leak that's less than half the size of a pinprick will do it. Over a several month period when mine was leaking, I had to add maybe a quarter of a cup of coolant. Smelled bad, and fogged up the windows, though