the 4x4 on my 2002 ford escape wont engage and work. turn the 4x4 on and it lights up but you hear and feel nothing engage or do anything

This on-demand all-wheel-drive setup only sends power to the rear axle when the front wheels slip. In the “4x4 Auto” mode, 100 percent of the torque is sent to the front wheels until a wheel slips. When that happens, a rotary blade coupling (RBC) generates enough pressure to activate a multiplate clutch, like that found in an automatic transmission, which sends torque (as much as 100 percent of it) to the rear. At the heart of the RBC is a “fan” with three blades in a chamber filled with a silicone fluid like that used in viscous couplings. The fan is shaped kind of like the warning symbol for radiation. When the front wheels slip, this fan spins through the fluid, heating and expanding it, which generates the pressure to activate the clutch. Then the clutch – not the viscous fluid – bears the burden of transmitting the torque. When set to “4x4 On”, an electromagnet energizes a small clutch pack, locking a ball ramp to the input shaft. Now when the wheels spin, they turn the ball ramp, which overrides the RBC and pressurizes the same multiplate clutch pack. In the “4x4 On” mode, the rear axle is engaged quicker and more securely. The front and rear axles are, however, never locked together except during front wheel slippage. That way there is never any crabbing or binding in tight turns, and there is no need for a center differential.