does the Webasto heater timer setting and programming function wear out or become faulty? I can make my Thermo top c turn on or off. But can’t make the preprogrammed settings work.

Yes, it is possible that a timer can develop a fault such as you describe. This particular timer model is no longer available, but if you let us know your heater model and build year we would be able to recommend alternatives.

Please send details of your heater and a brief description of your required functions of a controller to sales@butlertechnik.com

Thank you

Regards

David