Taking approx. 30 minutes using a phillips screwdriver and a pair of pliers, disconnect power source, unscrew (3) screws on rear of control panel, remove knob from front of timer switch, disconnected wires from back of switch, remove defective switch (type of quarter turn-spring clip holds switch in place), installed new switch (type of quarter turn-spring clip holds switch in place), reconnected wires to back of new switch (reverse of removal), install old knob on front of new switch, re-position control panel and re-install (3) screws in rear of control panel, reconnected power.