4x4 light comes on, but dosen't engage

[nickb]

I have a 91 explorer with stock 4x4 and today, while in the snow and not moving, I pushed 4x4 high and the light came regularly, BUT THE FRONT TIRES WERE NOT GETTING POWER.
After this, I shut off the light, by pushing the button again and turned it back on and it worked properly. is this serious? Wht do you think i should do?

 

[4x4Ranger]

It could be your auto hubs(if thats what you have). Try cleaning out your existing hubs or put Warn manual hubs on. They are much better than the auto hubs.