Another one of these heaters failed today with the water temperature sensor having corroded. The customer had reported a few fail to start issues a little while back and then complete failure, with the Webasto on/off switch reporting “lockout”.
The part number in question is 9010620A. Quite a tight thing to get to with the heater installed. It is also made of very soft metal, so be careful when removing and replacing!
With a plug in Webasto diagnostics, we could see that the temperature was reading 0c. Of course this wasn’t the case as even ambient temperature was 9c.
So after reading the fault, changing the component and then finally unlocking the heater, we were immediately back in business.