All my life I've used rocker/toggle switches that have had a light on them. One prong is ground, another prong is hot, and the last is for the accessory it's turning on.
I'm now gonna use some toggle switches that have no light on them, and there are only two prongs on them. Is one a ground and the other for the accesory? Or is one a hot and the other for the accessory?
On a three prong switch, is the power lead only for turning on the indicator light on the switch?
Please help...

 

ground and acc.

 

Thanks. I forgot the relay is already getting power directly from the battery.(right?) The switch just completes the circuit when turned on.

 

The switch completes the circuit. Hot going in from 12volts and 12 volts going out when the switched is flipped to the device you want powered. If you ground one side of the switch you will blow the fuse.

 

On the three prong with the light it only uses the ground for the light circuit. If you are using your 2 prong toggle to control a relay you are just sending 12 volts to the coil side of your relay to engage and disengage the contacts.

 

So on a two pronged switch that has no light, one terminal(prong) is hot, and the other terminal is for the accessory being turned on?

 

That is correct.

 

Yup just confirmed it with a voltmeter.
Thanks guys!