Fiddled with the old switch. Got high speed if I wiggled the one contact enough. So definitely the switch. Seems like that style of switch is hard for the case dealer to find. See internet is littered with them. I am no brain on this sort of stuff but is this switch with the resistors like a rheostat?
Sort of. A rheostat varies the voltage from low to high gradually. A resistor has a predefined out put. A switch with low/med/high would have two resistor wires for the low/med, and none for the high. I know my 2290 has a separate resistor. I'm assuming your 2590 is older as the Case parts site show the lower serial numbers had the switch with the resistor on it. If your dealer has the separate resistor, it wouldn't be hard to wire it in with the new switch you have.