Chevrolet Repair: 98 K3500 Front diff will not engage, transfer case, chevytalk

Question
The front diff will not engage when the transfer case is put into 4wd high nor does the 4wd light come on.  I replaced the switch on the transfer case and the actuator motor on the front diff. Power is coming out of the transfer case switch but the diff motor does not work. The 4wd light does work.   It has been 2 years since I have used the 4wd and now it does not work.  I have read this is computer controlled?? I need to diagnose further to fix the problem and do not know where to start. Can you help??

Answer
Here is a link to an upgrade for a slightly older truck than yours, but I think this is what you already have.

Computer controlled? I don't think there is any computer control.
But there may be an additional fuse and power source than just the one from the transfer case, because unlike the thermal one shown in this link, yours needs power to de-activate, since it is, in effect, a DC motor.
A poor or missing ground could also keep it from working.

I would like to see you go to Chevytalk, and post that question there.
It is a free site. And very helpful.

Here is a link from the site, where I am known as Fixitfox33.  Check it out.
http://www.chevytalk.org/fusionbb/index.php?referral/23610/

Van