I have a set of driving lights that I turn on and off with a switch right now, but I'd like to put a relay on them so they turn off when the brights come on.

Does anyone know if it'd be possible to hook up a relay to the wire going to the lights and send a wire from that to the bright wire so it opens when the brights are on?
I really still want to be able to control them from the switch besides automatically turning off when I put on brights..

To run the lights this way, you need to run a fused 12 volt(about a 10gauge wire)power source from the battery directly to the relay, you would run the two lights off of the relay. To activate the lights run a line from the low beams lead to the switch on the dash, than a line from the switch to the relay, this would be the trigger for the relay. This would allow you to turn the driving lights off when you wanted just low beams, and would switch them off when you put the high beams on.


If you wanted to be able to run the lights w/o the head lights being on, you couild run an additional switch and relay to the lights directly.

Thanks for the info, I'll go try to find a relay tomorrow and hook it up. I have a switch and wire from an old set of fog lights I can use as the second switch you mentioned too.. hopefully the wire from the second switch will be thick enough.

how about this?
bosch spdt relay

comes with a harness but the wire on the harness is 16 gauge..

Since it all comes as one the 16gauge wire might be fine. I usually use 10 gauge for main power to the relay, 12 gauge to each light, and use 14 gause to run the trigger wire to and from the switch. Though for $6 for everything it would be worth a try. If you had to go buy everything seperately it would cost you about $12-15, depending on where you bought the wire. I find buying the wire by the foot from a hardware store is cheaper than buying iot on a role at an automotive store.

I usually get the plain 5 pin relays from Autozone or Kragen's, they usually run about $5. You will need to get a box of female flat connectors to go with the relay.

JC Whitney also sells the complete harness.

Instead of a second switch or relay, I use a 3 pos. (micro = OK) switch on-off-on (couple $$ at radio shack) and run one side from headlite wire (hi or low, yer choice) and one side from 12v. The center wire would then go to 'trigger' described above.

I often use a double pole switch which allows me to run seperate indicator lites. For this, run 12v to the 'other' center, and a wire to a lite (then to ground) on each side. You can also parallel off output from relay for indicator lites, but that usually requires more wire (put the relay as close to battery and fog lites as possible). I have added LED's to dash near hi-beam indicator. <img src="/forums/images/graemlins/smile.gif" alt="" />

The size of the wire only matters battery to the relay and relay to lites. Bigger is better! The wires to and from switches and indicator lites should be small so they're easier to use and hide. These wires don't draw much power at all.

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