'91 with weird taillight problem....

I am checking a '91 'burban 1500 with a taillight problem. First, both brakelights, signal lights, and hazard lights went out in the rear only. When you would activate the turn signals (either one, left or right), from inside the vehicle it seems as tho nothing is wrong, the blinking indicators are flashing normally like if all bulbs are working. Outside the vehicle, only the front flash, the rear is dead. Same thing with the hazards, only the front. Driver took the truck to autozone (bad move) and they told him to get the brakelight switch, which he did.... it didnt fix anything. Fuses are good. I found a broken wire at the connector for the multifunction switch, turned out to be the right rear turn signal and brake light, put a jumper across the connector and now the right rear taillight is working. The left rear remains dead.

With the left turn signal activated, I probed and found the signal wire on the upside of the connector, signal good. Checked downside of connector, no signal, installed another jumper, now the signal is good on both sides of the connector, but still no brake, turn signal, or hazard on the left rear.

I opened the taillight housing and checked the bulb and contacts for continuity, ground is good, signal wire is dead.

Where does the wire go from here (bulb socket), and does it change color? If it does, where does it change and to what color??

I'm not sure if the 91's have the circuit board rear light system. If it does you could try re soldering or Napa has them in pairs for around $35.

I'm not sure if the 91's have the circuit board rear light system. If it does you could try re soldering or Napa has them in pairs for around $35.

no, they don't it's the old body style with the little square light...