GM-GMC: Right Brake/Turn Signal light not working, turn signal switch, signal elements

Question
I have a '91 GMC 2500 Van, right rear brake and turn signal not working - tail lights work when headlights are turned on.  I have checked the wiring with a voltmeter and I do not have any current running to the right side (DK GR wire).  Left side works fine - when I turn on the right turn signal - nothing happens in the rear and the front turn signal light lights, but does not blink.  Hazard lights work, and flash everywhere except right rear.  

Could this be a bad turn signal switch, or do I have a bad wire somewhere running from the switch/brake pedal to the right rear lights?  How do i figure out which?  

BTW, I know it's not the light bulbs.

Thanks, Ryan

Answer
Ryan,

The closest shop manual I have is for 1984. My answer is therefore a guess.

Since both the brake and turn signal elements are not working, I would check the wire for that element of the bulb.  The fact that the front turn signal element lights up indiactes that the turn signal switch is probably okay.

I had a fuel tank sender go haywire on one of my trucks.  I spliced in a length of new wire from as close to the tank to the dash (firewall side) that I could reach and my problems went away.  You might wish to try the same approach.