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!

[bd]

Do yourself a BIG favor!  Disassemble the ground connection you just serviced and liberally coat the terminal and sheet metal with some antioxidant paste available in the electrical department of most hardware stores.  Reassemble, ensuring the screw is tight.  This will help eliminate a recurrence.

[juancano]

I was thinking of that! Will do thank you.