Chevy Brake Light Problems

[Hunter Sousa]

Hello all. First I hope everyone is healthy and safe during this current pandemic. Meanwhile I’m having an issue with the brake lights on my 2006 Chevy 3500 Duramax dump truck. With all the lights on, when I step on the brakes, the brake lights do not “get brighter”. With the truck lights off, when I step on the brakes, the brake lights work fine. When I unplug the passenger side tail light, the rest of the lights work fine including the driver side brake light. I have the Rubbolite 8002 and 8003 rear lamps if that helps. Any advice on what it might be would be greatly appreciated. Thank you

[carkhz316]

This sounds like it could be a classic bad ground issue. I would visually inspect wiring, and check the 4-way junction box at the rear of the truck that the tail light harnesses plug into. Undo the connectors, check for corrosion or wiring damage. If none is found, plug them back in securely and try some voltage drop testing of the ground circuits. It sounds like with the parking lights on, that the ground circuit is getting overloaded when you go to apply the brakes. 

[Colossus]

Check those and check the wiring for trailer plug as well if you have it (chances are you do have the wires, even if you don't have a trailer light plug on your back bumper)  They can get corroded from road dirt and salts and other things and cause all kinds of issues. 

[jake111]

All of the above . . . plus try new bulbs.  Sometimes when they "burn out" the filament jumps over to another filament and strange things happen.  Sometimes you can't tell just by looking at the bulb, either.