https://www.yotatech.com/forums/f2/1...ctions-119070/

I've install some factory fog lights and followed the steps in the thread listed above. However, the thread uses a two prong switch and i have a 3 prong switch. When everything is hooked up the switch will not illuminate when it is turned on. I've tried grounding it. I know the switch is good becoause I swapped it out in emergency light set-up i have (firefighter). I've tried just about every combination that i can think of to try and get that dang little orange light to come on but i can't figure it out. Any help?

 

I have no idea if it is specific to those lights but usually 3 prong switches will have
one for power in
one for power out (those two make the circuit)
one for ground

so as long as you are using those three (correctly) it should work fine.

does the switch not say anywhere what is ground? it might call it earth or something

 

I know what each of the three prongs are...that's what's weird. I hooked the switch up to another application and everything worked fine. It must have to do with the fact that i'm tying into the factory wiring in a situation that originally would not have used a lighted switch.??.

 

Not sure of the specific switch or wiring you have tried, but Toyota typically uses a switched ground wiring design on the lighting circuits. That means there is constant power to the light then the switch grounds the light out to make it turn on. Problem is that most 3-prong lighted switches assume that the light bulb inside is tied to the ground connection. Thus the switch has 1 light prong, one for +12V and one for ground. You might be able to run the switch backwards, that is hook the power and ground up backwards. Otherwise, get a switch with a separate light and try that.

 

I'm using the oem illuminated fog light switch. I think you are correct. I wired it up backwards and the light came on...but it stayed on no matter if it was switched on or off.

 

if you play around with it a little more, I believe you should be able to get it to work