2006 Sierra. I’m bolting in two extra cargo lights in the bed of my truck. I want them to come on when I hit UNLOCK on the key fob. Easy enough as I can tap into the reverse lights which already come in while unlocking.
How can I do that PLUS have a dash switch to turn them on from inside when needed?
Im not afraid of electrical mods, just running into a mental roadblock.
(there is the option of one light for the first scenario and one for the second but I’d really like to use both lights for both jobs)
When you currently turn on your interior dome light does the exterior white light come on to illuminate the truck bed?
In reply to John Welsh :
I have this button on the dash. Bottom is fog lights and the top turns the cargo light on.
But now that you ask, I’m not sure that cargo light comes on with unlocking with key fob or not. So, no. The dimmer/dome light switch doesn’t turn on the cargo light, it has the separate button seen below
Curtis
UltimaDork
4/21/19 10:30 p.m.
Relays are your friend here. You can supply the power from switched or hot (your choice) and tap into the reverse/cargo circuit on the load side. Then supply the switched input from the same switched or hot, and run the trigger side out through a switch in the dash to ground.
When you turn the switch on, it grounds the relay sending juice to the circuit.
I did this exact thing on an old pickup I had. I hid a switch up under the bedrail that took hot power and tapped into the reverse lights with a relay. I used it for light when I was hitching a trailer in the dark.
Here is a super quick diagram of what I did. I know relays don't look like that nor are they wired like that, but it's late and I've had two Chardonnays. In your case, you may have some issues with back-feeding voltage. For instance, the key fob that unlocks the door and makes the lights flash might have some connectivity to something that makes trouble. Like if you flip the dash switch and it feeds juice to the circuit, will it also unlock the doors? Or will it cause the panic mode to start? Know what I mean? Modern vehicles with all their computery stuff needs some extra attention to detail. If it would cause a problem, a diode might be in order to prevent feeding 12v back to something that confuses the truck's brain.
In reply to Curtis :
That was quite an answer thank you!
I may just end up wiring one to the cargo circuit and one to a new dash switch. I’m not AFRAID of electricity but I don’t think I’m knowledgeable enough to make your plan above work.
I looked at a similar idea for my ham radio - and decided that a SPDT switch on the signal input side of the relay was the best way to approach it to prevent inadvertantly backfeeding voltage onto the run wiring. slightly different application but similar theory. Tap one voltage supply off the existing reverse light supply and one voltage supply off a key-off hot. Run the single output from the switch to the relay signal input. Main power to the relay is a fused hot wire. For bonus points you can jumper the fused hot for the relay to the fused hot for the switch if they're close.
So the idea is you leave the switch on the position that signals the relay when the reverse lights are on, but you can flip the switch to turn them on at any time.
Secondary thought - I wouldn't want bed lights on when I'm actually backing up because theyd probably blind me to what was behind the truck. Unless you've got a bed cover.
