How to Wire 3rd Stop Lamp in Camper Shell on 2021 Ford Ranger  

Question:

Expert Reply:

The # C58345 4 pole trailer wiring harness wouldn't be a good option, as the brake lamps and turn signals are carried on the same circuit. If you installed it that way, your 3rd brake lamp would blink along with the turn signal as well as illuminating with the brake pedal.

There are a few ways to do this.

The easiest way to do this would be to pull the 3rd brake lamp housing out of the rear of the cab and use a circuit tester like # PTW2993 to find which wire carries the brake lamp signal, and use a quick splice like part
# SWC502905-1 to tap into that circuit for the camper shell third brake lamp.

Another option would be to locate the BCM (body control module or computer) located under the dash to the left of the steering column. You'll want to find the wire for the CHMSL (center high mounted stop lamp) which is yellow and gray. There are a series of connectors attached to the BCM, you'll be looking for connector 5, the yellow/gray wire should be coming out of pin number 13. Once you locate the wire, you can use the appropriate quick splice to tap the feed for the camper shell 3rd brake lamp into that wire.

If the 3rd brake lamp on the camper shell is NOT an LED, you can use a vehicle to vehicle taillight converter like part # 118158. On the INPUT side, ground the white wire, tap the yellow wire into the left turn circuit of the trailer connector, tap the green wire into the right turn circuit of the trailer connector. The red wire on the OUTPUT side of the converter will provide a 'clean' brake lamp circuit that won't make the 3rd brake lamp blink with the turn signals. The yellow and green wires on the output side won't be needed, you can simply cap those off.

expert reply by: Mike L

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