Elektrik: Spareparts for Webasto heater in 750 iAL (09/2000)?

[AnttiS]

Hello!

Webasto is factory installed Thermo Top Z/C. Now, I would need to know if it is "bus contolled" or "traditional (voltage controlled)" one? If it's traditional I would consider to replace its controller with an aftermarket sparepart. The thing is that BMW only replaces the whole heater unit. They don't sell spareparts!!! However, Webasto dealers sell also controllers but they don't sell BMW specific models.

Before replacing the whole heater (which is damn expensive) I would like to try to replace its controller only.

Any ideas?

Antti