Relay and Switch Wiring for Light Bar

ChibbMD

ChibbMD

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Dec 29, 2021
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47
Location
Dallas, TX
I seem to be on a roll with electrical projects. Tonight I'm trying to change up the way my front light bar works. Currently, it is wired into the low beam headlight circuit, but it still has a switch in the cab. So basically, I turn the light bar on/off with the interior switch, but only if the headlights are on. Here is how it is currently wired:

1. Fused wire from the battery positive to relay
2. Negative terminal of the battery to the relay
3. One terminal of the interior switch to the relay
4. The other terminal of the interior switch is tapped into the low beam wire
5. There a power wire coming out of the relay running to the light bar

I would like the light bar to operate independently using the interior switch and not have it linked to the headlights. This would allow me to use the light bar in any circumstance whether the Jeep is running or not. I think this is a very minor change in how the interior switch and relay and connected, but for some reason I can't deduce how to do achieve this. I think everything stays the same except the wire running from the headlight wire to the switch, but if I disconnect it, where does it go?
 
Wire from switch to headlight circuit needs to be rerouted to be switch to battery power. The switch is supplying power to trigger the relay. Currently it is using headlight power to do so, so the relay won’t trigger with the switch unless the headlights are on. With that wire run to battery power instead, the switch will always be able to trigger the relay at any time, thus giving you full control of the light bar at any time.
 
machoheadgames said:
Wire from switch to headlight circuit needs to be rerouted to be switch to battery power. The switch is supplying power to trigger the relay. Currently it is using headlight power to do so, so the relay won’t trigger with the switch unless the headlights are on. With that wire run to battery power instead, the switch will always be able to trigger the relay at any time, thus giving you full control of the light bar at any time.
Click to expand...
Yes, that is the correct wire to change. (the control voltage coming from the headlight circuit) There are a few ways to wire it.
You could also wire it [switched] from the ignition circuit, so it kills the lights with the ignition switch.

(IMHO) A better way is to;
Hook the control voltage up to either + or ign [unswitched]
then run the ground wire under the dash and [switch] the ground. (on the control side of the relay, not the load).
Switched grounds are safer and cleaner to run. If the circuit shorts out, the lights just turn on. no damage done.
Good luck

ground rtigger.jpg
 
Last edited:
Thanks guys. So last night I decided to play around a little and moved the switched "trigger" wire off of the headlight wire to a slot on the interior fuse block that had constant power (I think it was my empty CLOCK fuse). Worked perfectly. I did wonder if I could tap the switched trigger back into the fused positive wire and the above diagram (and Macho's input) confirm that.
 
Yeah you can do it any number of ways really. Many different ways to control the relay and the light circuits to make them do what you want, how you want it.
 
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