GMC 4wd actuator problem?

My 4wd front axles won't engage I put 12 volts to the actuator and It moves. NO power detected at the actuator leads so I
does anyone have any idea where the 4wd fuse is located?
since the actuator is working and no power seems to be going to the actuator, its either a fuse or a sensor. There's a sensor above the actuator and IM not sure what it does or how to test it. Im thinking that might be whats causing the actuator to not be powered. does anyone have anyother ideas what might not allow power to go to the actuator??????????

If it is late 80's to early 90's there should be a sensor on top of the trasfer case that will send signal to acuator when put in 4 wheel drive inside. The sensor above the acuator just sends a signal to the light on the floorboard. If you have the old thermal acuator and have to replace it you will want to upgrade to the later style servo motor style.

The fuses should be in the interior fuse panel. Check the 4WD and Transfer case fuses