The four wheel drive went out in my brothers S-10 its a push button set up. the light comes on when you push in the button and it kicks into low gear when its pushed but the front end wont engagehe said there was no pop or bang before it quit working it just quit,i dont know anything about them so any help would be greatly appreciated.

 

are they strictly electric with an electric motor to engage it or is it vacum operated does anyone know