It’s a diesel or petrol coolant heater. My E60 530d have Webasto thermotop C heater, Google it! When i start my webasto or use timer, inside the car blower motor turns on and starts blowing warm air inside and the water pump circulates coolant to the engine and interior heating cell. And when you are driving the webasto gives your car more heat to heat up faster. It shuts off when coolant temperature is 80°C and starts again if coolant temperature drops below 70°C. Best thing in winter for diesel cars! Last week in Finland we had -35°C🥶

 

I couldn’t remove the codes from webasto but all other modules like CAS i was able to delete codes.

 

It is an auxiliary heater that is an option on Euro cars. It has a fuel line to the main fuel tank and you can heat the car with the car engine off. If you go to Realoem and look up your car and then switch it over to a EUR model and then to Heating and scroll down to Auxiliary heating.

 

Oh ok. That's why I've never seen or heard of it. I saw it had something to do with Aux heating but mine only has an aux fan. It makes sense now.

 

By the way, how do you heat up your cars before starting in the parts of US that have cold temperatures in the winter? Do you use block heaters or other auxiliary heaters?

 

My cars are parked in the garage