4X4 won't lock

My buddy has a 1994 4x4 regular cab and long wheel base with a V6 motor (179,560 miles) and we went in the woods last weekend and the 4x4 wouldnt lock in (it worked the weekend before perfect) i think this could be an actuator on the front differential ?? i am going to check all the little things first this weekend though....is that actuator about the only electric 4x4 part ??? because his has the shifter on the floor for the 4wd thanks for helping again !!!

Could be the front actuator, check for power at the actuator connector, if there is no power at the wires with it in 4x4, it could be the switch on the transfer case

Definately the front actuator....just had the same problem and this fixed it within 1 hr.