When a front defroster stops working, it's usually a faulty switch or blend door if air comes out of the other vents or a bad blower motor if no air comes out of the vents.

What can I do if my defroster doesn't work?

Solution: When the engine and radiator are cool, top up the coolant. Then warm up your vehicle and see if the defroster starts working better. If the coolant level is low due to a leak, have a mechanic find it and fix it.

What causes the defrost not to work?

A bad heater core will result in no heat, which means a non-functioning defroster. ... If the blower motor is malfunctioning, the defroster will not work. Issues can range from a blown fuse to a bad blower speed controller. The blower motor itself can also go bad and need replacement.