Something wrong there then, I’d put a proper fuse in and see if there is power to the switch.
if the switch is goosed you can get one of these mk3 controllers, the switch is basically the same just upside down on the other side. I used one to fix mine.
https://www.heritagepartscentre.com/uk/1h0820045c-fresh-air-and-heater-controls.html