Will flour damage a car AC?
I'm trying to prank my brother. I'm going to pour flour down his AC vents and turn it all the way up so that when he turns his car on, the flour flies out everywhere. The only thing I'm worried about is this damaging his car. Is there any way any of the flour would somehow stay in there and damage something? Thanks 
Comments
It would be very bad. A/C evaporators normally have condensation (moisture) on them in operation, which will attract residual flour and form a paste that will never come off. Worse, it will gradually corrode pinholes in the evaporator so the evaporator will have to be replaced sometime in the next year. The cabin air filters that are standard today came about when pollen was corroding pinholes in evaporators after the change to R134a.
You don't mention make, model, or year, but figure between $700 and $2000 for repair.
Better to use baby powder. Flour will get sticky from the humidty and be really difficult to clean up. Either way, I'd think of a different prank. Like the potato or banana in the tailpipe.
Or let the air out of one tire and the spare tire if you have to do something, this is safer and easy to fix.
Good Luck!.