Its sounds to me that you have the same
problem i have. basically the heater wheel makes contact with copper strips which are in a circular arrangment. It sounds to me that they are not making contact correctly. Can you get speed 1-3 work if you press in, or go slightly between two speeds? I have only 2 work, have to press in for 1 but it cuts when i release, 3 is at 3.5 and 4 is just past for. Need the wheel of and clean all and adjust the contact piece