I would have thought it must have a trigger pressure at a specific level but that must be pretty low, so you could be right Lightspeed. I know that mine never comes on with the engine running, even when the oil is very hot and at idle with a pressure indication of 22 psi on the SPA gauge.
It isn't my cars switch that has failed but I was asked by another owner if I knew which switch it is and I don't know the exact Harley equivalent to the S&S item. The S&S 106-0744 is only $21 (if you can get one) or £46 from Morgan! The HD items are more readily available at a more reasonable price, the main reason for the Alternative Parts List.
