Temperature gauge non functional

I have a 1994 GMC sierra Truck, 131K, 2WD, 5.0L 3/4 ton. I cannot get any reading on my dash temperature guage. It moves when started (moves all the way to the right, then back left). I've replaced the sending unit on top of the engine next to the thermostat housing, AND the single green wire sender on the drivers side of the engine. Still no temp. reading. What else am I missing? Thanks in advance.