TM 10-3930-659-20 1-13. SERVICE BRAKE SYSTEM (Con't). e. Wheel  Brakes.    The  wheel  brakes  are  a  wet  disc-type  brake  arrangement.    When  hydraulic  pressure  is routed  to  the  brake  pistons  via  the  brake  valves,  the  pistons  move  outward  and  compress  the  brake  disc  against  the stationary backing plate, slowing or stopping the forklift truck. f. Parking Brake.  The parking brake mechanism is mounted on the transmission.  The actuating pedal and release handle are located in the operator's cab.  A red light flashes and an audible alarm sounds if the parking brake is applied while the engine is running and the transmission is in gear; a yellow light flashes if the parking brake is applied and the transmission is in N (Neutral). 1-14. STEERING SYSTEM. a. General.  The steering system is a full-time power assist-type.  A secondary electrically operated pump is included  to  provide  emergency  steering.    The  other  components  of  the  system  are  the  steering  valve,  cylinders,  and crossover relief valve. b. Main Hydraulic Pump.  The main hydraulic pump supplies the steering system only.  It is mounted on the transmission and is driven by the engine.  It is a fixed displacement, external gear-type pump. c. Secondary Steering Pump.  The secondary steering pump Is electrically powered.  It operates when the key switch is In the ON position and low steering system pressure is sensed by a pressure switch. 1-15. FORKLIFT HYDRAULIC SYSTEM. a. General.    The  forklift  hydraulic  system  includes  the  service  brake  system,  steering  system,  hydraulic reservoir, and attachment components.  The service brake and steering systems are described in paragraphs 1-13 and 1- 14.  The attachment components consist of the forklift control valve, oil cooler, and two oil filters. b. Hydraulic Reservoir.  The hydraulic reservoir is a 20 gl (76 1) tank, located just ahead of the engine. c. Forklift  Control  Valve.    The  forklift  control  valve  controls  the  operation  of  the  forks  for  boom  raise  and lower, tilt, and spacing. d. Oil Cooler.  The oil cooler is mounted alongside the engine radiator and cools both the hydraulic system oil and the transmission oil in separate sections. e. Oil Filters.  There are two filters that are contained in the hydraulic system.  The hydraulic reservoir suction filter, located at the hydraulic reservoir, filters larger contaminates and uses a washable screen.  The hydraulic oil return filter  contains  a  bypass  valve  and  a  replaceable  cartridge-type  filter.    It  filters  contaminants  entering  the  hydraulic reservoir from the components of the system.  Should the hydraulic oil return filter become clogged, a hydraulic oil filter restriction switch will light and the bypass valve will open. 1-16. ELECTRICAL SYSTEM. a. Charging System.  The 24-volt charging system consists of the batteries and an alternator with an internal regulator. b. Lighting System.  The lighting system is protected by a circuit breaker and contains two front driving lights, an  adjustable  floodlight,  two  rear  cab  mounted  worklights,  front  and  rear  turn  signals,  taillights,  a  domelight,  front  and rear blackout lights, and instrument panel lights. 1-9