HS800 2WD to 4WD switch

[PRoy]

Hi,  I have a 2013 HS800 and all of a sudden the switch to go from 2WD to 4WD does not work.  When pressed/changed over it just stays on 2WD and won't go into 4WD. 

Any idea on cause & how to fix? TIA guys.

[cliffyk]

The switch, wiring, differential servo motor and/or differential gears are bad--repair/replace the bad component(s)...

I apologize for the terse response, however it's the best I can do given the information provided.

Does it (the front differential or anything related to 4WD make any noise when you operate the switch--KOEF (Key On Engine oFf)?

If not, have you checked the 4WD fuse (usually a 3 A device)?

[PRoy]

The switch works, fuse are good, the light comes on to show 4wd is on.  No noise heard on the front when the switch is pressed (unlike the unlock button when pressed for the rear 2wd). I have power all the way to the block on the front differential so it tells me there is the problem. Thoughts? Does it make sense that could be the cause,?

[cliffyk]

Here's a YouTube video describing disassembly of the front differential, and some info re: how the 4WD solenoid works. THe guy is a hack, working on the floor--in a video presenting removal of the differential he uses a 16 oz. claw hammer.