I bought a house with an older Thermador Waste King under counter trash compactor. The seller said it did not work. The operating switch is a rotary removable key style with three positions-- off..on..start. If I hold the switch to the start position the unit operates and runs through the cycle. If I let go of the key, the unit stops at whatever point in the cycle the ram is in. Do I understand that typically you turn these switches to start and let go and it automatically runs through the cycle and shuts itself off? I pulled the switch and it has a cam on the back side the turns with the turning of the key and engages a door lock pin. The number on the switch is 639-852023-1. It seems to me that the switch is broken but I have no part number other than the above number that is printed on the switch body. It looks like the cam comes off and would be installed on a replacement switch. Is this switch mafunctioning and if so is a replacement or equivalent available?

Thanks in advance
Rick in CT