I'm working on putting in a manual fan switch. The switch I have has three terminals: supply volts, on acc., and earth ground. I know the ground is connected to ground, but where should I connect the other two? If at all possible, I would like to also like the switch to be in parallel to the current curcuit. Any help would be appreciated.

 

ok one should go to a 12 volt source and the other goes to the load that you want to turn on, so just take the the positive from your source and plug it into the switch then find a 12 volt source and plug it in to. depending on if you want it to turn on when the car is on or off. hope this helps

 

be careful with that light up switch... i had one if its whazt i'm thinking and it literally melted right through... after that i used a heavy duty switch..
as for your power, i hooked the power right up to the battery then i hooked the thrid to the pigtail of the real fan switch located on the passenger side of the block