I have a 94 chevy silverado 4x4. before I got the truck, someone wired a 3 position toggle switch under the steering column. it is wired in between a small gauge purple wire. It doesnt seem to do anything that I can tell, and the truck runs good. I dont have accesory or fog lights, and the purple wire goes into the wiring harness, like at one time someone was bypassing or testing something. just dont know what, and dont have a wiring diagram.. any help much appreciated.

kill switch maybe? flip it and see if it still starts. I glanced at the wiring harness schematic and it shows the purple wire to go to the fuel pump.

How many terminals are on the switch, and which ones have wires attached?
Is it possibly a switch that disables the cab lights? Some sportsmen want this to avoid ruining night vision when they arrive at a destination. Flip the switch with door open to find out if it kills the cab lights.....

it has 3 terminals and 2 wires. I read somewhere that purple goes to ignition, so I dont know if they were trying to make an anti theft setup..
I will try the cab light test.

ok I did some tests and the toggle switch does not control the cab lights.
With the IGNITION switch in the off position there is no power to the wires. when the switch is turned to assesory or cranking and running there is a pulse voltage of 24.65 vdc to 15.09 dc to 0.12 dc. these 3 pulses happen repeatedy very quickly.
turning the mystery toggle switch in any position does not kill the truck.

Im now wondering if the previous owner was having a problem with the ignition switch at one time, and they wired the toggle switch in to activate "" the assesory function ? then when they had the ignition switch fixed, they just left the toggle switch there?

Is the pulsing im getting on my meter the fuel pump cycling on and off ?

ive had some intermittent battery drains, and dont know if somehow that switch is the culprit.

Have read of people installing a switch to keep the torque converter in the locked position for use during towing.

it could go to the muffler, or not. well it could.

Could be one of these:

http://www.bing.com/videos/search?q=jame...2CA0F1AB4915A64

Hook up the fuel pump to a DSO and see if the voltage cycling you get on the DMM matches what you see on the DSO.

Dad had a 72 Chevy that had belonged to a Sheriff he had a toggle to kill the brake lights, we assumed he used it to "spy" and did not want the brake lights flashing.

Dad knew that when he bought the truck otherwise we may have driven with out brake lights then the toggle was flipped!

Good luck and update us!