Mud & snow switch ?

Sounds like the switch may be bad if it returns to the original position when not held. It's either an inter axle lock or an axle lock. If the later use caution when using since an axle lock will cause your drive axle to act like a solid axle and will not allow one side to turn faster than the other. So on dry pavement you could loose some of your steering response.

 

which is why it's a temporary contact switch meant to be used as an emergency thing and not let ingaged

 

I would rather have a light on the dash, remember if this engages during spin-out (IE: one wheel spinning and one not) you can count on damage. It's kinda live popping the clutch on one wheel.