I have a 1994 Chevy Silverado K1500. The Brake lights are intermittent. The cab brake light always works. The rear brake lights will work for awhile after unplugging anything in the brake system or plugging the trailer into the adapter. The turn signals and the flashers always work. Is there some sort of capacitor in the system like for the flashers that may be bad?

 

sounds like someone has messed with the harness. i had similar problems in my 95 k1500 and later found out that my harness was hacked to hell and back. anyways welcome to truck forums!

 

sounds like the rear harness is messed up. try unhookin the trailer adapter and just plug the lights back in.