wow, they must have changed that in 91, my switch for the light was attached to the vacuum motor attached to the axle.
when mine is on, the shift fork has moved the axle disconnect into the connected position, the light can be on, but the x-fer case would still be in 2x4. none of the engine power would be going to the front axle due to the x-fer case would not be sending it, but the front drive shaft would be rotating due to the front wheels rotating.