i have a 2002 ford ranger 4x4,4.0v6. i am having problems with 4wheel drive.its like theres no power to the switch at all. the fuse is good on bothe sides.mechanical wise it worked great,just lost all power at once

 

Check the shift motor on the t-case. They seam to be a common problem.

 

The 2002 Ranger 4x4 system relies on several different electrical components. As such, there are several fuses you need to confirm are good:

Battery junction box (underhood) fuse#:
1 (50A)
3 (50A)
13 (20A)
30 (10A)

Central junction box (inside cab) fuse#:
28 (7.5A) (manual transmission)
10 (7.5A)
11 (7.5A)
5 (15A)

And as noted, it could also be a TC motor issue.