on my 08 screw lariat with the auto hvac system. i always use auto and just set the temperature and its always worked fine. well several times now out of nowhere the windows will completely fog up, to the point i have to pull over. i have tried a couple things when it happens, turn the air down to 60 on full blast, tried heat full blast. but nothing clears it right up, once i get it cleared up thought it goes back to normal.
anyone ever had this problem? im thinking thinking the ac might be low but havent had a chance to check the charge.

 

Normally when you get window fogging like that it is a heater core leak. it also normally leaves a sweet smell, from the coolant. Don't know if coolant still smells sweet, with most all of it being long life, or not. Hope for your sake it's not that because that's an expensive, or terrible, job. The only other thing I could think of is if you have a water leak to the inside and there is water hiding in the carpet or elsewhere. Under the right conditions it will make itself known in the way you describe.