Brake light goes off and headlight dims when front brake is applied

[Guest]

Does anyone have an idea on my brake light is going OFF and my headlight significantly dims when my front brake lever is applied? I don't think the problem lies within the brake lever circuit.

I think I mixed up some wires when I recently upgraded the little L headlight to a 7" bucket. Do these symptoms ring a bell with anyone?

Thanks!

[Big T]

Well, it comes from your brake light switch. So:

1. The switch is corroded inside (very common)
2. There's a short in the switch wiring
3. You hooked up the wiring wrong

Whatever, when you activate the switch, it's sending power to ground

[Steve]

Another possibility is a loose ground wire in the tail light.

Without a proper ground, the tail light (the dim filament) will ground out through the brake filament without lighting the brake light. When you apply the brakes, there is now power coming down the wire, and, since there is no differential at the bulb, the tail filament goes out.

Why it's dimming the headlight, I don't know.

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