84 GMC silverado swb 4x4
so noticed the other night that my left tail light wasn't working. Bulb is good but ground wire was rusty, cleaned ground for good contact. Looked underneath and found main problem, 3 broken wires were they were spliced for the fifth wheel trailer harness. One wire was for rear tail light, one for side tail light, and one that ran to the brake side of rear bulb. so ran some new wire and connected everything back up and i have no brake lights. Im thinking they havent been working for a while now, but tail lights work and turn signals work just fine, witch is even wierder as the turn signals and brake lights use the same filament and even the same damn wires other than the ground and both of those are good.
so if there is any body out there that has delt with these before, what am i missing? I have gone through and check continuity and voltage and just cant find the hole. BTW the right tail light assembly is after the left one in series.

thanks
nick

check the brake light switch that is connected to the brake pedal under the dash. see if it has power