my truck window always fogs up?

If your passanger side floor is wet/soaked, replace the heater core............the rest of these ideas are a waste of money.........hows the fluid level in your radiator................use your jacket sleeve if nothing else..................stick your head out the window...............

If the RainX didn't work, I don't know what will. Try applying more of it. Otherwise, you've just got to get the defroster fixed. RainX is the best as far as chemicals go that can keep it from fogging up, so if that failed the only possible way to keep it clear is to have the defroster working.

Wether your defroster works or not, if your heater core is leaking it will put a film of antifreeze on your windows when it gets warm and keep coming back. Because it is sort of oily it is hard to get off. If there is an oily film on them, the only solution is to have the heater core replaced.

besides as perchance having a bypass situation including your defrosters,Crack open a window slightly and make effective your glass is sparkling interior.dirt attracts moisture.try "invisible Glass air purifier",cleans the pores of your glass so glass maintains to be air purifier longer.

Are you using windex to clean your windows? Next time try warm water with some vinegar - no residue.

Is it possible there's water coming INTO the car while it's parked? (old seals, for example, can cause this)

just roll the windows down a little.