Webasto Thermo Top Pro 90 Fault

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!

Left: Corroded temp sender. Right: New temp sender.

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.

Diagnostics showing 0c – clearly faulty.

So after reading the fault, changing the component and then finally unlocking the heater, we were immediately back in business.

Faults cleared and temperature reading correctly.

Simple!