Those damn relays and 3-way switches!

[zwiks]

Hello, I have a homemade off-road buggy. I have two set of light, one set on the roof and one set on the front bumper. How can I do the wiring, so I can use a on-off-on (3-way) switch to either turn roof AND bumper, OR just the bumper lights on?

 

[tgootee]

The "on-off-on" only tells you that the switch is double-throw, with an off position in between the two throws. But it doesn't give any information about the number of poles. A 1P2T on-off-on would have one common conductor that could be connected to either one of two separate conductors, one per "on" position. You could use a double-pole (i.e. "two pole") version, a 2P2T with on-off-on, which is like two separate 1P2T switches within one switch.

With a 2P2T on-off-on, you could run the + battery terminal to both of the "common" center terminals, so that it would connect to the two "on" conductors on whichever side the switch is thrown toward. Then on one side of the switch, only use one of the terminals, for the bumper lights. And on the other side, use both terminals, for both sets of lights. The other sides of the lights will just connect to the ground, or back to the negative of the battery, and aren't involved with the switch.

Make sure that your switch is rated in terms of DC current and voltage, at some healthy safety margin above the current that your lights will actually pull.

 

[kam1787]

Make sure that your switch is rated in terms of DC current and voltage, at some healthy safety margin above the current that your lights will actually pull.

If the lights pull more than an amp or so it would be better to get a switch that has screw type connectors - use a spade lug on the wires.

- - - Updated - - -

Make sure that your switch is rated in terms of DC current and voltage, at some healthy safety margin above the current that your lights will actually pull.

If the lights pull more than an amp or so it would be better to get a switch that has screw type connectors - use a spade lug on the wires.