'92 Sierra XC 4X4 is inop, two different actuators

[dwcopple]

had the Dorman Electric with harness and that worked for a while this winter, but, I routed the brown wire in a poor spot and it got chewed up and shorted. I cut that part of the wire out and made it butt connect and got 12V power again. However, the 4x4 won't engage. I warrantied the electric Dorman out through Amazon and ordered a new thermal unit like it had from stock. Just installed that and it won't work either. Checked the 4x4 illum fuse and it was good, but the 4wd 25A fuse was blown. Put in a new 25A fuse in that slot and still no 4x4. WTF??? Help me please. Oh, and yes, I pulled the steel spacer thingy out of the diff when I went back to the thermal unit.

 

[KansasOBS]

Isnt the thermal unit just a two wire? I cant remember offhand, but there are videos on yt that show the pinout of the actuator.

If you can bench test the units, to double check them. And if you're getting 12v to the pin that needs it on the truck. Then there has to be an issue mechanically in the differential. Id imagine you can hear the actuator, I know I can on mine.

 

[dwcopple]

Nothing wrong mechanically. It's definitely electrical. The 4x4 doesn't even light up. I watched a video to test the plug harness for the actuator for 12V. If it's dead, then it's the Tcase switch. (Which looks absolutely horrible location to remove of course)

 

[dwcopple]

UPDATE: the new T-case switch (Dorman from O'Reilly) fixed it. 7/8" wrench to remove the old and tighten the new. 4x4 works again!