Brake lights dont work with DRLs on..

[HotWheelsBurban]

So the bulbs were indeed installed incorrectly, and noticed they were rusted on the inside, so I went ahead and replaced them.

Now, the driver light works perfectly as it should. The passenger light, the brake light is dim, and when the running lights are on and I press the brakes, the lower running light turns off and I don’t have brakes, but only on the passenger side.

I noticed a red neck job of splicing the trailer connector so I went ahead and ordered a new wire harness for the lights and will remove the trailer harness to see if that works.

Do you still have stock style taillights with circuit/socket boards? Those get loose connections and do weird things....

 

[GoToGuy]

The turn signal and the brake light are the same filament ( wire in bulb ) when turn is active it is flashing the brake light circuit.
A dim filament that should be bright is wrong wattage bulb, poor grounding, bad socket, round base bulb installed incorrectly. Brake and turn are BRIGHT they are telling you something important.
You can order new tailight assembly's on Amazon, complete with bulbs. I recently ordered got a pair for the K2500 Silverado as they were starting to get hazy, and some age cracks. $ 50 for a pair.
Good luck!