ARMY TM 9-6115-671-14 AIR FORCE TO 35C2-3-446-32 MARINE CORPS TM 09249A/09246A-14 2-12   TABLE 2-4.  DIAGNOSTIC CONTROLS AND INDICATORS (continued) KEY CONTROL OR INDICATOR FUNCTION SPEED CONTROL UNIT 10 OVERSPEED indicator (red LED) This indicator is normally off, even when the generator set is operating.  When the LED is lit, an engine overspeed condition has occurred (the flywheel RPM sensor has sent the speed control unit a value which is defined as out-of-tolerance).  The indicator will remain lit until either of two events has occurred:   (1)  The OVERSPEED RESET pushbutton has been manually activated, or (2) the generator set (engine) has been stopped and the DC power is reset. 11 ACTUATOR indicator (green LED) This indicator is normally lit when the electric actuator (on the injection fuel pump) has power applied to it.  The LED will be lit when the engine is operating or when the engine is being cranked (started).  If the indicator is off while the engine is operating, it can mean:  (1) the electric actuator has failed, (2) the connection between the actuator and the module has failed, or (3) the module has malfunctioned or failed. 12 SPEED SENSOR indicator (green LED) This indicator is normally lit when the engine is operating.  The indicator lit/off function is directly related to the signal from the speed sensor connected to the flywheel.  If the indicator is off, but the engine is operating, this indicates the engine RPM signal is not being received.  This can be caused by sensor failure or by a failure in the connection to the sensor. 13 OVERSPEED RESET pushbutton If the OVERSPEED indicator is lit and the engine has stopped, this switch may be used to attempt to reset the overspeed protection system.  If the OVERSPEED indicator turns off when the switch is activated, the protection system is reset, and the engine may be restarted.  (The conclusion is that no problem exists with engine speed.)  If after restarting the OVERSPEED indicator comes on again and the engine stops, there is a problem with engine speed control. 14 OVERSPEED TEST pushbutton This switch is used to test one of the protective systems of the generator set:  engine overspeed protection.  Pressing this switch while the engine is running at rated speed will activate the overspeed protection system, thereby stopping the engine. 15 DC POWER indicator (green LED) This indicator is normally lit when the engine is operating.  It indicates the internal DC power in the module is operating. 16 CRANK TERMINATION (green LED) This indicator is normally lit when the engine is operating.   When the engine is being started, the indicator will remain off until engine speed exceeds 400 RPM and the cranking relay returns to its normal (non-energized) state.  If the indicator remains off and the engine starter continues operation, this is an indication of a failure in the starter assembly or of the cranking relay. BACKPLANE MODULE 17 LED 16 (red) indicator (not assigned) 18 LED 15 (red) indicator (not assigned) 19 LED 14 (red) indicator Fault indication.  If indicator is lit, indicates a fault has occurred.  If off, indicates normal running condition.