Do I need a relay with an LED light bar?

[getlost4x4]

I just installed a 40 LED 3 watt/bulb light bar. its supposed to pull a maximum of 120 watts. The equivalent of 10 amps, max.

I wired my light bar up just like i would for any other auxiliary light. I used a 4 pin 40 amp relay to power the light. For some reason i cannot get the light bar to fire up with the relay in there. I've checked and rechecked my wiring numerous times. Everything is wired correctly and i have good grounds. I'm also running two fuses inline with the wiring harness.

When I remove the relay and run the power straight through my switch, the light bar fires right up and works fine. The wires do not feel like they are getting hot in any way.

I installed this on my Toyota Sequoia today.



Testing tonight

 

[Gooseberry]

Its just insurance. I had 2 hella's that came on the van and the wiring was ok but the switch did get soft after a few hours. So when the rigid light bar came with one I used it and by doing so shortened the wire length and kept the current out of the cab.

 

[obscurotron]

Stupid me, but did you make sure that the output on the relay is energizing when you flip the switch? Relays go bad. Only had it happen once, so it's not common and not something most people check. They figure if they can hear the relay "click" it must be OK.

 

[getlost4x4]

i have two brand new relays. i'm not sure, but i cannot hear either one clicking.

 

[getlost4x4]

well, it appears i have solved it. I was using a 12V source from one of my parking lights. It must not have been able to supply enough power for the relay. I switched it over to the headlight and now i have enough power. The relay is working and the light is now running off the relay.

Thanks for the suggestions.

 

[colodak]

your constant hot 12v source should be from the battery, the trigger should only come from the high beam or switch

 

[Hilldweller]

your constant hot 12v source should be from the battery, the trigger should only come from the high beam or switch

The highbeam would be best since you want those retina-scorchers to turn off when you flip to lowbeam.

 

[kingg5]

im having the same issue, i ran the 12v switched for the relay from the cig lighter in my 2013 jk. two led cubes will not light up, would you say that the spot i used is not sufficient? Not sure how to tap into headlight wiring.

the light on the switch does light up.

 

[robert]

Use your volt meter and check the voltage at various points along the system, you're probably not getting enough to the relay. Most vehicles could really stand to have heavier wire run to everything, but especially the lights.

I'll have to see if I can find the website, but there's a whole page where the guy varies the voltage to his lights in small increments and measures the light output. It was pretty surprising how even small drops can really effect your light output.