stebs
Junior Member
- Joined
- Nov 10, 2012
- Posts
- 10
- Reaction score
- 6
- Ram Year
- 2012
- Engine
- 6.7 cummins HO
I needed to tap into the cargo light feed to switch some lighting i added to a work trailer, so heres what I did.
The cargo light gets its power from the cluster. It is a white wire with a tan stripe that is found in the 43 pin harness to the left of the brake pedal inside the cab, and is pin 22 i believe in that harness (its right next to an orange wire). The wire went along under the door sills on the drivers side.
I poked an 18ga wire through the grommet that the parking brake cable goes through in order to get the wire outside the cab. From there, i zip-tied it up to the harness that goes clear back to the trailer plug.
Since the cargo light gets its power from the cluster, I quick-spliced a fuse holder onto the wire under the door sill panel, and butt-spliced my 18ga wire to the fuse lead. I fused this at 2 amp since it was the smallest ATO fuse I could find in my area. At the other end of my 18ga wire, i spliced in a diode (radioshack #276-1103), and then spliced my relay connection to the other end of the diode. (note: I also taped a short piece of 10ga wire alongside my first diode connection to add some strength) I also strapped a diode across the relay coil as well to use as a suppression diode (reverse polarity)(google diodes on relays for details) to stop the back emf that occurs when relay coils de-energize). I used the diodes to protect the cluster when the coil de-energizes. I then provided ground by just bolting a ground wire through an open hole in the frame.
The truck also has an add a harness on it to add a 7 pin plug inside the bed for a gooseneck trailer. I cut the B+ wire in the add-a-harness and put my relay there, so that the relay switches the B+ on and off. I had to go by actual pins on the harness instead of wire color because the add-a-harness used different colors than the truck wiring.
Here is where I quick-spliced the fuse holder in under the doorsill. The grommet for the parking brake is near the right side of the pic. The fuse holder is hard to see here, but it is right below the red butt splice at the top left of the pic. The brown wire is my new wire that I added that goes clear to the back of the truck.
Here is the relay spliced into the B+ wire on the add-a-harness. The white wire is my relay ground wire that goes to the frame.
So now, I can switch the power to the B+ terminal on the 7 pin trailer plug by turning the cargo light on and off. If you wanted to add lighting inside your bed, You could tap off of that B+ wire that goes to the trailer plug, as it is hot all the time, even with the key off (it is fed by the 40 amp trailer tow fuse)
The cargo light gets its power from the cluster. It is a white wire with a tan stripe that is found in the 43 pin harness to the left of the brake pedal inside the cab, and is pin 22 i believe in that harness (its right next to an orange wire). The wire went along under the door sills on the drivers side.
I poked an 18ga wire through the grommet that the parking brake cable goes through in order to get the wire outside the cab. From there, i zip-tied it up to the harness that goes clear back to the trailer plug.
Since the cargo light gets its power from the cluster, I quick-spliced a fuse holder onto the wire under the door sill panel, and butt-spliced my 18ga wire to the fuse lead. I fused this at 2 amp since it was the smallest ATO fuse I could find in my area. At the other end of my 18ga wire, i spliced in a diode (radioshack #276-1103), and then spliced my relay connection to the other end of the diode. (note: I also taped a short piece of 10ga wire alongside my first diode connection to add some strength) I also strapped a diode across the relay coil as well to use as a suppression diode (reverse polarity)(google diodes on relays for details) to stop the back emf that occurs when relay coils de-energize). I used the diodes to protect the cluster when the coil de-energizes. I then provided ground by just bolting a ground wire through an open hole in the frame.
The truck also has an add a harness on it to add a 7 pin plug inside the bed for a gooseneck trailer. I cut the B+ wire in the add-a-harness and put my relay there, so that the relay switches the B+ on and off. I had to go by actual pins on the harness instead of wire color because the add-a-harness used different colors than the truck wiring.
Here is where I quick-spliced the fuse holder in under the doorsill. The grommet for the parking brake is near the right side of the pic. The fuse holder is hard to see here, but it is right below the red butt splice at the top left of the pic. The brown wire is my new wire that I added that goes clear to the back of the truck.
Here is the relay spliced into the B+ wire on the add-a-harness. The white wire is my relay ground wire that goes to the frame.
So now, I can switch the power to the B+ terminal on the 7 pin trailer plug by turning the cargo light on and off. If you wanted to add lighting inside your bed, You could tap off of that B+ wire that goes to the trailer plug, as it is hot all the time, even with the key off (it is fed by the 40 amp trailer tow fuse)