Ford Repair: 1994 f-150 4wd, automatic locking hubs, sensor signals

Question
My 4wd is not working on my truck. I have automatic locking hubs with a push button on the dash. When I push the button I can hear a click in the dash near the glove box, but nothing else happens. The 4wd indicator light does not come on and the hubs do not engage. What is wrong and how do I fix it?

Answer
Check fuse 17. Check all related connections and grounds. If you hear a click, the module is most likely ok, most common failure in these systems is the motor. If the module does not receive correct sensor signals from the motor, the light will not come on, and the module will not activate the motor.