Cargo Light Wiring

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stebs

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Im needing to add a relay to the back of the truck and i'd like to have it operate with the cargo light using the switch inside. Where is the best place to tap into the feed for the cargo light at on a 2012 3500 Laramie Megacab?
 

jlb

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I don't know where the harness actually runs for said light, but I would expect it is almost exclusively inside the cab. I would probably start by removing the light, and trying to get a look at where the harness runs, although I am sure it will be primarily between the inner, and outer sheet metal components.

I like the idea though. You should post up some info on where the best tap the wire when you wrap up the project. Sounds useful! lol
 
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stebs

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I'll keep ya guys posted.

If I end up tapping inside the cab, whats the best way to get the wire out of the cab to the back of the truck?
 
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stebs

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Just an update. the cargo light apparently gets its power from the cluster. the wire that feeds the cargo light is white with a tan stripe (labeled "cargo lamp driver" on my diagram), and is apparently pin 22 in the 43 pin harness to the left of the brake pedal inside the cab. So now, i need to figure out how im going to get a feed back through the firewall, which im going to try and poke it through with the bundle that already goes through. My initial plan is to t-tap that wire there, add a small fuse and then go through the firewall and route my way back to the tailgate... I'll keep ya'll posted
 
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stebs

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Okay, Got it done. I tapped the cargo light wire (noted in previous post) in the drivers door under the doorsill. used a quicktap or whatever its called and tapped in a fuse holder with a 2 amp fuse. Then i ran an 18ga wire through the bushing that the parking brake cable goes through, and zip tied it up to the harness that goes to the back of truck. There I put a relay, with a diode before the relay and a diode across the relay coil. I cut the B+ wire in the add a harness (7 pin for gooseneck) and placed the relay in there (the relay switches the B+ to both 7 pin plugs now). I had to go by pins instead of wire colors because the add a harness used different colors than expected. This way the only place i've touched factory wiring is at the quicktap at the drivers door.

Heres the tap at the drivers door. The buttsplice (top left) is connecting the fuse holder to the 18ga wire to the back of the truck.
IMG_20121120_160128.jpg

Heres the relay at the back. The white wire with yellow connector provides ground for the relay coil.
IMG_20121120_165308.jpg

I also added another relay on the trailer that is switched with the running lights, so now, when we're using the trailer at night, as long as the running lights are on, we just hit the cargo light button and the worklights on the trailer come on. :head3:
 
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