PTC Heater (Electric Auxiliary Heater)

PTC stands for positive temperature coefficient: the resistance of the ceramic elements rises as they heat up, which limits their temperature. In combustion cars it sits in the heater box and helps until the engine is warm. In electric cars, high-voltage PTC heaters warm the cabin or the battery.

Current through the ceramic elements generates heat, and the self-limiting effect prevents overheating.

PTC heaters draw a lot of current, so cars often switch them off when the battery or alternator is under strain. In electric cars, heating with a PTC uses more energy than a heat pump and reduces winter range.