Jeff i'll bet someone has installed turn indicators at one time or another. There should only be 2 wires to the rear of the truck. One from the park lamp switch to the tail lamp and one for the stop lamp. (fused 6V to brake lamp switch and then to the brake lamp.)
Did you do the long wire check? Run a wire from the negative side of the battery all the way to the rear of the truck and use it to ground your test lamp. Then check you wires for power with the test lamp. Do you now have power with the park lamps in the on position? Do you have power with the brake pedal pushed? If no then we most likely have a wiring problem on the power side of the cricuit. If yes you have a ground problem to the frame. (needs a ground from the battery negative to the frame)
I didn't do it, no one saw me do it, you can't prove anything! "Bart Simpson"
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