In article , ml
wrote:

the switch has 3 legs labled

gnd

load

power

ML-

What is the Radio Shack part number? I would have assumed the same as
you. I wonder if the switch might have been assembled with the labels
backwards?

With the switch in the OFF position there should be an open circuit
between Power and Gnd, and lamp resistance between Load and Gnd. With
the switch in the ON position, Load and Power should be shorted, and
lamp resistance between either and Gnd.

That is assuming the lamp is intended for 12 Volts. If it was intended
for 120 Volts, it most likely would be a neon lamp in series with a
resistor, and would measure as an open circuit.

Fred