Brake Lights turn off if I have my lights on

[juancano]

1986 C10 2WD

I've had a similar issue before but this is new.

Right side tail light: Brake light works when pedal is pressed; if I turn the lights on, the light on the tail light turns on (same bulb, 2 filaments). But, if the lights are on and I press on the brake, the bulb just turns off. So no light and no brake light.

- Replaced Bulb, tried 3 different bulbs
- Replaced socket (previous one was also a newish one)

What could it be? The brake pedal switch? Ideas?

[bd]

The bulb socket isn't properly grounded to frame.

[juancano]

I will quadruple check that. Thank you.

[bd]

Try using a temporary jumper wire between the socket shell and a shiny bare metal spot on the frame (not the bed, since the bed may not be properly grounded due to corrosion or a broken ground lead).

[juancano]

Sonnnofa..... it was the ground.

The ground is screwed to the body (sheet metal) with a metal ring and a bolt. I undid it and noticed it was kinda rusty. I sanded the terminal and the part on the body clean, and now it works.

IDK why I don't check for that kind of stuff first. It seems it's a bad ground 90% of the time!!

Thank you all for your help!