If it's on your Westmorland VW, chances are it's the relay mounted to the driver's side of the airbox (cars with AC). I've found that the switches rarely go bad: at least, if it works on one speed, it should work on all 4.
Or, the resistor on the pass side might be bad too. There should be an AC cutoff/temp sensor mouted to that side (it should have a long probe coming off it and going into the box), and then there's the resisitor. They rarely go bad though, so I'm suspecting it's the relay.
If you have a NON-AC box, then it can only really be the relay.
Good luck finding one. I don't think they're available aftermarket. It's a dealer-only item if it's even still available.