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Ford F-150 Camper/Shell 3rd Brake Light Wiring

Tools Needed:

Pliers
Wire stripper tool (or scissors)
Scissors or side-cutters
15mm or 5/8 socket & ratchet
8mm socket & ratchet
Multimeter or voltage meter
Soldering iron
Electronic solder
Safety glasses

Parts Needed:

Camper/shell/canopy with 3rd brake light installed (LED or incandescent)
1 set male/female wired connectors
Small diameter plastic wire loom (optional)
Two or three plastic tie-raps or zap-straps
1/4inch diameter heat-shrink tubing

Parts Cost:

$5.00 , if you need to purchase a 3rd brake light it could be $20-50 depending on how fancy you want to go.

Theory:

Nearly all Ford F-150 trucks made in 1997 and later have a 2 light taillight system. This can't be easily wired into a 3rd brake light because you need a logic circuit to somehow only turn on the 3rd brake light on your camper shell when the brakes are applied and not flash with either signal light.

Fortunately Ford has included a light green wire in the rear bumper wiring harness exactly for this purpose. It isn't connected to anything. It comes from the switch on the brake pedal before it goes to the "multi-function" switch that makes the logic for the tail/turn lights. It is actually meant for mounting a 3rd brake light on a camper/canopy or if you have a large travel trailer with a 3rd centre-mounted brake light.

Make sure you use your safety glasses while under the vehicle to avoid dirt dropping into your eyes.

Procedure:

Follow my instructions completely at your own risk. I take no responsibility for any accuracy in my instructions.

if your camper or canopy shell 3rd brake light isn't wired already you will need to run two wires from it. A positive and a negative down to the driver's side of the back of the box where the taillight area is. To this you will need to solder and fasten a connector that can be quickly disconnected in case you need to remove the canopy.
first you need to locate the light green brake light wire under the rear bumper/frame. Start at the wire loom coming from the driver's side taillight. Follow it from the outside of the vehicle to about 8 inches from where it drops down from the taillight. You'll see an electrical connector. This is where the main harness plugs into the rear harness. Disconnect it. Pull the main harness wire down but towards the trailer wiring harness on the inside of the frame. This way you can pull it down more than pulling it down by the taillight side.

Photo of wiring harness at rear of the truck

You'll see the green wire about 8 inches from the end of the harness coming out of the main wiring harness wire loom and taped back to the main harness. Separate it from the harness. This wire isn't going anywhere and is simply for future use. Make sure you have the correct wire.

Photo of the main wiring harness (look for the light green wire)

Strip the end of it off and leave 1/2 inch of bare wire.
Make up a two conductor wiring harness that will go from the hole in the box by the rear taillight down behind the taillight and comes out below the taillight in the frame area. Make it a couple feet longer than necessary to reach the green wire because you need to find a suitable ground location.

Photo of soldering preparation
Photo of cutting the wire
Photo of the connector
Photo of heat shrink procedure

Solder the connections and apply heat shrink tubing to seal the splices (above).
Fish the new connector wire into the hole in the box and down through the back of the taillight (remove the taillight with 8mm bolts - 2 bolts, then pull to the rear of the vehicle to remove).

Photo: Insert the connector through the hole in the box... Photo of wiring behind taillight Photo of taillight removed, fishing wires through the hole

put a tie-wrap on the new wire so that it doesn't fall into the box hole when you don't have the canopy on the truck and the wire disconnected. Shown below. Note: Make sure the white wire on the connector shown in the picture below is the positive... the reason is when it's disconnected you want the insulated part of the connector touching your bed/box surface so it doesn't short out.

Photo of plastic zip-tie on the wires to prevent them from falling through the hole

Strip the wire which will attach to the green brake wire and slip some heat shrink tubing onto the wire. Then twist the bare conductors together. Solder the connection. Tape up with a bit of electrical tape. Slide the heat shrink tubing over the joint and use a match or lighter to seal it. As shown above when we made the new connector cable but each wire is separate down below.
Locate a suitable grounding spot on the chassis. I used the large bolt that holds the 4-prong trailer connector under the bumper. Strip off about an inch of your new connector ground wire. Twist it straight and apply a good coating of solder so this wire will not corrode. Loosen the bolt with a 15mm or 5/8 socket/ratchet and put your ground wire under the trailer wiring bracket. Tighten it up. Pictured below.

Photo of ground wire and connection

Here's what it looks like when finished. Kind of crude but you can always use longer wires and more tie-wraps if you want. Just don't let your wiring hang below the bottom of the bumper or it will look ugly.

Photo of finished wiring job

Here's what it looks like during the day. Hard to see the 3rd brake light in this picture.

The final product! Success!

That's it. Your done and it looks cool, plus it's safer.

On my canopy there is also an electrical connector on the passenger side rear corner just like the 3rd brake light connector. I'm saving the other half of that quick release connector to eventually run a power wire for the dome light inside the canopy.

Editors note: I know what some of you are thinking, there are already 3 brake lights in the F-150. Well, that's true, technically this is a fourth brake light ;-)

This article has been generously donated by Peter Ferlow.