3 Way Switch Powered By Relay
 

I have a dump trailer with a three way switch powering auxiliary lighting. But now I would also like to tap into my reverse lights on my truck to power a relay to power the aux lights. So is there a way to have a relay to power a three way switch for lights?

I am not sure what you mean by a "3 way" switch. If you have a simple switch that turns the lights on and off, you can add a relay and tie it into the same wire going to the lights after your switch. When you turn the switch on, power will go down the wire to the splice, go on to power the lights and go backwards up to the new relay and do nothing, the relay will be off. If you happen to turn the backup lights on, the relay will send power down the wire also, the two power sources will bump heads, still powering the lights, no harm done.

If you turn the backup lights on, the relay will send power down to the lights, and also backwards up to the switch where it will stop. Same as before, if you happen to turn the switch on at the same time, the power will just be coming from two sources, they will still power the lights.

I'm confused, since the aux lights already have power, why do you want to add a relay to power lights already powered?

The lights are turned on by two three way switches built in to the trailer I would like to keep that ability and somehow add a relay to power the lights when i put the truck in reverse.

Ah, piece of cake.

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