All is well now. I disconnected the truck battery. Disconnected the brake switch connector and installed a jumper wire. With a spare battery I back fed electrical current on the dark green wire from the rear of the truck. The problem was in the half moon connector under the dash. Just as "Roadmarks" suggested, there was minor corrosion. I cleaned the terminals with a detail brush and applied a skim coat of dielectric grease. Ready to roll.
