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How can I connect light bar turn signal lamps?

2008 Expedition XLT

Light bar has two unused rear-facing yellow lamps.

We want to connect them as turn signals.

Are there wires under the dash to which we can connect the light bar turn signal wires.

Otherwise, we must go through the firewall and connect to the wires leading to the turn signal filaments.

Thank you,


Hope it works, good luck. This could be easy. All I seem to learn about electricity is to expect surprises.

Going through the firewall would be my choice, there should be an existing path for wires with room for a couple more. Under the dash is cramped to work on and will probably involve tearing apart a wiring harness.


You are correct.
I can fit more wires through the firewall rubber plug through which I passed the siren speaker wires and light bar power wires.

I don’t mind working under the dash in cramped conditions.
I would prefer to open a wiring harness INSIDE and find the correct wires - if they are accessible and not too tight.

Is there a wiring diagram on line which I can view?

Thank you.

In the fuse box above the radiator, there are two relays which send power to the trailer plug to operate the trailer brake lights and turn signal lamps.

It would to have the relays send power to the rear yellow light bar lights.

However, both relays close when the brake pedal is depressed.

Is there a way to cut the brake wire from also operating both relays and illuminating both yellow lights?

If I could view a wiring diagram, I could determine which wire to cut.

Thank you.