Another possibility is the heater resistor pack has failed (which will likely be by-passed on position 4)....
At least I know now not to do it on my own caryou have no thermal overload protection so something else will burn instead!
The little component that sits on the top of the green block is a 'thermal fuse' rather than another resistor. If the whole green unit gets too hot, this 'fuse' fails (by melting inside)... which is why, Trimdoner, it worked on all speeds once you'd bypassed it. However, note that 'next time' you have no thermal overload protection so something else will burn instead!