Seat Mii Auxiliary Heater Problem

I had a similar issue with my Seat Mii. The parking heater refused to start. It turned out to be a faulty glow plug in the auxiliary heater. Before replacing it, did you check the error codes using an OBD2 scanner? It should give you some indication of what is going on.

Thanks for the quick response! Yes, there was an error stored related to the auxiliary heater, but it only mentioned a general malfunction. Glow plug makes sense. Was it difficult to replace? Did you also check the temperature sensor while you were at it?

I didn't do the repair myself. I let the workshop handle it, as I did not want to risk damaging the heating system. However, if the error code points to the glow plug, it is likely the culprit. The mechanic mentioned that a defective glow plug is a common issue. I recommend taking it to a workshop.

Big thanks for the help! Dropped it at the shop, and you were spot on - glow plug on the auxiliary heater was indeed defective. The temperature sensor was also checked, and thankfully it was fine. All in with labor and parts came to 440€. Expensive but at least the car heater works again! Hopefully no coolant leak in the heating system for a while.