If you have a scematic then there is some hope. You should be able to see if a relay is involved or not.

Peter is correct. You should measure the voltage at the switch:

First, put the red lead of the meter on the incoming power contact of the switch and put the black lead on a known good ground. Measure the voltage with the switch off. It should be at least above 12V. (It should be whatever the battery voltage reads).

Now push the switch and see if the voltage drops and how much. Normally it shouldn't drop much. maybe 1/2 volt. If you see a larger drop then you need to trace the path from the battery, through the fuse, connectors, relay if any, etc. If the voltage doesn't drop then you need to look at the ground side of the circuit. If I had the schematic I could hopefully give better advice. I remember on my 86 Supra, the passenger window had a switch on both doors so the driver could control it also. And the switches were wired together in kind of an odd way. I had to study the schematic a while to figure it out. In that case the swicth on the drivers door needed repair.

__________________
1998 C230 330,000 miles (currently dead of second failed EIS, yours will fail too, turning you into the dealer's personal human cash machine)
1988 F150 144,000 miles (leaks all the colors of the rainbow)
Previous stars: 1981 Brava 210,000 miles, 1978 128 150,000 miles, 1977 B200 Van 175,000 miles, 1972 Vega (great, if rusty, car), 1972 Celica, 1986.5 Supra