Hello.

I brought this truck with a over sprayed 3rd. Brake light.

Ind that case i brought a new one from ebay. (Led with the cargo light).

The new led light i got, does not work when talking about the red part. The only thing that works is the cargo light.
i have checked the light and it works fine, so its some kind of wiring malfunction.

​​​
I followed the wire from the 3rd. Down and can see the white/brown/tan colored wire is cut by the brake switch. Have tried bypassing the wire to the other but does not work.

I'm currently lost...

Please help. Best regards Robert Siemssen 🤔🧐

 

LED lights don't always work well in some places. They are polarity sensitive, I.E. if they are hooked up backwards, they don't work.

Verify you are getting power there when the brakes are applied.

 

I have checked the wires up by the roof. It only have power ind one of the wires. And it's power All the time.

 

Grab the service manual for your truck from here. Wiring diagrams are in section 8W. Not sure if the switch is supposed to supply power, or ground on that circuit...... FSM will know though.

 

Is the 3rd. Brake lig supposed to stay on or only come i. When i push the brake?

Btw thanks for the link. But i dont know s***t about electricity.

 

You'll learn. Wontcha.

Light should only come on when you step on the brake.

 

Anyway. I was playing around with the wires and found out that the wire by the lamp, that had constant power is for the Cargo light.
light. And that the light switch turns on the ground and therefore lights it up.

I found out by taking the wire with current and the one with ground i could make the red part light up.
Therefore i know which wire goes to the brake pedal. And that it need to provide the 3rd. Brake light with power.

That wire I'm talking about is on the picture. Its the wire thats cut.

 

Splice it back together, see if it works.

 

The white/tan wire should be pin 2 which now has the decidedly non-factory green wire connected. The white/tan wire powers the CHMSL as well as the rear brake lights so it's a bit of a mystery how these do work currently. You need to figure out where the green wire goes, brake controller maybe ?

 

Perhaps I'm doing something wrong but I've searched that manual via your link and have yet to find any results for third brake, third-brake, or 3rd brake. Any suggestions for isolating that circuit?