Truck Repair: 4X4 wont engage, case locks, selector panel

Question
I have a 1994 GMC Sierrra.  When I lock the four wheel drive in, the light on the selector panel does not light.  It feels like the transfer case locks in, but the front tires do nothing.  I pulled the actuator out of the front diff and wired it straight to the battery. It seems to be working this way.  I also checked the lead wires running to the actuator with a test light.  With the vehicle started and the transfer case engaged and have nothing.  I would appreciate any help that you could give me.


Jammie

Answer
Hello Jamie,
The actuator is quite often the problem, but so far, you have checked and eliminated it. Good job.
I will say I might have checked the fuse first, but then again, with the history of actuators, I may have done exactly what you have done.

So...check the fuse first.
Then go to the underside of the body.
Over under the floorboard, about under the passengers seat, way up on top of the transfer case...kinda squeezed between the top of the transfer case and the floorboard, there is a little switch...sticking straight up.
There is a plug in that switch with two wires.
One wire comes from the fuse, through the ignition switch. It is supposed to be hot when the ignition switch is on.
When the transfer case is shifted to 4X4, that switch closes, and sends power through the other wire to the actuator.

If you did some serious off roading, that switch and plug can get damaged due to shifting of the body, etc.
There is a connector on the right rear side of the front axle in that circuit, that could be unplugged if a stick catches it.

So do the fuse, then follow the wires to and from that switch.

After the actuator is powered, and operates, then the 4X4 light will engage, from a switch on the front axle.

Van