While the auxiliary heating of the coolant also needs the standard fan or an additional fan with a relatively high battery load to heat the interior, everything is already integrated in the auxiliary air heating (picture). However, the engine is not preheated here, which makes this device more suitable for mobile homes and truck cabs with sleeping spaces.

The interior of an auxiliary air heater is similar to the one that heats the water, only in some magnification. There is again a fan that blows in the air tangentially this time to create air vortices. Fuel is added in doses and the whole thing is ignited in a secondary chamber by a glow plug surrounded by a metal fleece until the combustion is stable enough.

The liquid fuel is normally adapted to the existing one, namely gasoline, diesel, but also bioethanol. If such an additional heater is installed in a purely electric vehicle, it sometimes even has its own small tank. If the driver forgets to refuel, the only thing missing is the heating, driving is still possible. No more restrictions due to lack of electricity.

In 1953 there was the first Eberspächer air heater in the VW Beetle. Due to its air cooling, there was no way to heat the engine anyway. At the same time, its very economical heating, initially even possible with an oil smell, provided enough arguments for warming the air from the outside.

From 1970 this heating could then also be installed in the interior. The advantage here was that reasonably clean air was always sucked in, because the normal Eberspächer heater did not have an intake filter, but which in dusty use, e.g. in construction machinery, has severely attacked the bearing of the fan. If this slowed down, there was coking in the combustion chamber and thus further damage.