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How to wire light switch thru acc instead of battery

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chiuchimu

10+ Year Contributor
94
3
Jun 25, 2008
Sylmar, California
2G Eclipse 1997 GS

I've accidentally drained my battery at least 3 times in ten years. What I would like to do is have my head lights turn off when my ignition is off. That way I can't leave the light on accidentally since I always remove my keys from the car.

I have an ACC wire at my radio that is easy to splice into. I want to use it to power a relay. The relay will go before the light switch power wire - hence even if the light switch is left on, the relay will go off once ignition is off and kill the lights.

Where is the easiest place to splice into the light switch power source?
Wire color, position on fusebox or light switch wire harness would help.
 
Well the headlight relay is in the fuse box under the hood, if I wanted to do this I would provide power to the coil side of the relay only when the key is on. Should be pretty easy to do. Im kind of assuming that the headlight switch provides a ground for the relay coil to turn it on. If its the other way around its basically the same thing.
 
Or you could make all your connections right at the headlamp switch since your gonna be right at the ignition switch anyway. I would find a normally open relay and wire it into you head lamp signal wire, and have the relay close when the ignition is on or accy. Just keep in mind that if there is a problem with the relay or circuit it will not allow you to power on your lights or if your are driving they will shut off. If I where you and wanted to have a feature similar to this I would buy a timer to latch a relay on until the time expired and would then drop the signal inturn turning the relay to its "normal state" which would be normally open and turn off the lights, that way its a little safer.
 
Or you could make all your connections right at the headlamp switch since your gonna be right at the ignition switch anyway. I would find a normally open relay and wire it into you head lamp signal wire, and have the relay close when the ignition is on or accy. Just keep in mind that if there is a problem with the relay or circuit it will not allow you to power on your lights or if your are driving they will shut off. If I where you and wanted to have a feature similar to this I would buy a timer to latch a relay on until the time expired and would then drop the signal inturn turning the relay to its "normal state" which would be normally open and turn off the lights, that way its a little safer.

Good point. I should set up a bypass switch so that if the relay fails, I can switch on the bypass and the wire goes straight to light.

Anyone know the light switch wire color at steering column harness?
 
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