TM 9-2320-386-10 2-6 2-3. CHASSIS CONTROLS AND INDICATORS (Contd) Key Item and Function 1 Seat spring tension adjustment handwheel is turned to adjust the driver’s seat spring tension to the operator’s body weight. 2 Horizontal control lever is pulled up to adjust driver’s seat forward or back- ward. 3 Windshield wiper control knob turns windshield wipers to LOW, HIGH, or OFF position. 4 Air reservoir drain valves are opened to release air pressure and moisture from air reservoirs. 3 4 1 2