Water temp guage not working, no signal to guage, new sending unit, signal to truck computer but nothing after that. Tried new guage also.

I need year--make--model to look up wiring info?

On most vehicles there is a water temp sender unit for the temp gauge and a water temperature sensor for the computer.
for the gauge the power comes from the power source ( ignition switch) through the gauge to the sender unit, through the varying resistance in the sender unit to ground( the hotter the water the less resistance--the more reading on the gauge )
if the wire to the sender unit is disconnected or the power through the gauge is stopped( broken wire , loose terminal , fuse,etc), then the gauge will not read
test by placing the wire to the sender directly to ground , turn on the ignition and if the gauge and circuit is correct, the gauge will immediately go direct to hot
as for the temperature sensor, that has up to 4 wires connected, has nothing to do with the temp gauge but reports to the ECM with the water temperature so that the ECM can make the changes to the air/fuel mixture ( cold -more fuel as in choke to operating temp for correct mixture ratio to overheat to put on the engine light and go to limp mode)
when the parameters of the sensor unit are reached or exceeded, the ECM then switches the relay for the fan to cool the radiator and after that to put on the MIL light