Wiring question

hello,

So I am wiring up a light bar or two. I want to be able to have them turn on with the brights, that part is easy. I also want to be able to turn them on individually without activating the othe other, is there an easy way to do this? Would a diode on the relay trigger achieve this?


Thanks

 

no, you can do it by running the switch across the relay contacts​

 

Thank you for the reply. so if I understand correctly, you are saying run a split of the high beam through a switch to the post on the relay for the LED?

 

You will need a diode between your high beam wire splice and the relay coil. A 1N5400 should suffice. Just be sure your control wire from the switch is downstream of the diode. That will allow you to turn on your LED bar by either turning on your high beams, or by turning on the switch. Downside is there is no way to turn off the LED bar if your high beams are on. I can show you a wiring diagram if you want.

 

I understand what you want, my question is, why not just wire them individually with a toggle switch, on their own circuit? Then you have control of when you need them on without any extra diodes, relays, wire taps, etc. Your truck will function as designed from factory, if you need the light bar on, flip a switch.
The added bonus is, if something electrical goes wrong with your truck, they can't say you caused it by tapping into the wiring system. The CAN/BUS system on new vehicles are sensitive and I highly recommend any accessories be on their own circuit, protected, and switched individually.

 

hes using the high beam to trigger a relay, that in turn is driving the "added lights" so if 2 and 10 are the coil driven by the high beam then 3 and 5 is the relay's "switch" driving the added lights put a switch between 3 and 5. A diode is the wrong approach.

 

Not sure what you mean by 2 and 10, and 3 and 5.

If I understand OP correctly, he wants his LED bar to come on by one of 2 means: turning on his high beams, or by turning on his switch on the dash.

 

Cosmics got the theory down but daddyo has the right idea due to warranty claims.

 

yup typically terminals 2 & 10 are the coil, 3 & 5 are a normally open contact. So take terminal 10, attach to ground. Take terminal 2 and attach to one of the highbeam supply wires. Take terminal 3 attach to appropriate fuse, attach other side of fuse to battery. Take terminal 5 attach to "external lights". Make sure relay contacts are rated for double the current draw of the "external lights" (this is for logevity of the relay contacts). I'll draw a cad drawing once I figure out LibreCad for linux.

 

Ah I gotcha. Although he will still need a diode to isolate his high beam circuit. I drew a quick diagram, didn't include any fuses for simplicity. Maybe you're thinking of a different way to wire it.

 

I am, no diode needed. erase dash switch put across switch in relay. Remove diode

 

put the fuse close to the battery between the switch and battery

 

Why not dual relays? Fuse to taste.

 

He would have to run heavy gauge wire into the dash, find a switch rated for that high amperage, and the run another heavy gauge wire all the way to the LED bar. Your normal dash switch is rated for like 4 amps max. He would also have to increase his wire gauge to a bigger size because of the added resistance of all that extra wire. I'm talking 10-14 gauge wire instead of 22 gauge, depending on the draw of his LED bar.

 

jake has the right idea dual....good idea.No large gauge needed. How much current does a lightbar pull anyways 8-10amps? if so then 14/16guage thhn should be just fine.

 

2x 40A relays for $10 done.

 

Caliraised bar is rated at 25 amps, but I personally haven't measured if it pulls that much.

I'm not quite sure why everyone is against using diodes. It is by far the simplest way of achieving what OP wants to do. Since you already have to run the wire from the high beam to the relay, you would just splice it in-line and heat shrink, and you'd never know it was there, like the picture. .