I was wondering if this is possible... I want to install a 4 inch retangular LED light in the cargo area of my 4runner. I'd like to control it both by the existing Rear Deck switch in the dash and by a new rocker switch mounted in the cargo area. I would like for it to turn on when either switch is turned on. The wiring I'm envisioning is that each switch is on its own circuit with its own ground. The power leads going into the light would be joined. Is this a safe way to wire this? Thanks in advance!

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Clarification - I'm not going for a 3 way set up. I simply want either switch to power on the light: either or both on - light turns on; both off - light turns off

Should be a switched ground setup...just t-tap the ground circuit between the light and the stock switch and extend it to your second switch. That way it either switch can complete the circuit and having them both on would be the same as only having one on.

Edit - if it is a switched power setup, running another power feed to the light would be fine.

Thanks BMcEL. Can you elaborate on your switched power comment? I'm not clear.

The 1st gen 4Runner deck light is wired like that. The front deck light switch and the rear switch behind the roll bar will turn the light on and off. Only gotcha with the factory setup is it requires the parking lights or headlights to be on before the deck light gets power. So I rewired the front switch for constant power and then spliced in an external plug into the rear deck light so I could plug in some other light. I use a 12v LED trouble light strapped to the roll bar for a deck light. Unfortunately the FSM wiring diagram does not show the full wiring for the 4Runner (they only have the pickup setup with one light and one switch). I suspect it is set up as a three way light switch:
- http://home.howstuffworks.com/three-way2.htm

Tapping the rear deck light for an external plug:


That white wire runs to a 12V lighter plug into which I can plug a 12v LED trouble light on the roll bar plus an LED festoon bulb in the deck lamp:


My old camera does not take good pictures in low light, but it is very useable light in back and with the LEDs, it can run for hours w/o draining the battery.

Thanks. I plan on rewiring the front switch for constant power as well - so the existing wiring is not important. I'm just curious what happens if I run two power feeds from two separate switches into one light - will that cause any issues?

There should already be a second switch in the back for the deck light, unless you are talking about adding a 3rd switch. All depends on how you want the switches to work, one option is have all the switches in parallel so any one on turns on the light. But you'll need to have all the switches off to turn off the light. Or wire them all in series and then you need all the switches on to turn on the light, but it'll turn off if any switch is off. Or do the 3-way switch wiring like shown in the link above. I suspect that is how the factory wiring is done. I just re-powered the dash deck light switch from constant 12 volts and I can turn the rear deck light on and off with the dash switch or on and off with the rear switch.

Yes. Parallel is what I'm going for. I've gotten rid of the existing cargo lamp and fabbing a new set up. I'm ok with all switches being off to turn off the light.

Still unclear on what the proper schematic for parallel looks like.

You'll just want to be sure and power both switches off the same power source so that if both are closed, that are not cross feeding between two different circuits.

Awesome! Thanks again. No matter how I searched Google, I could not find a schematic for this.