TM 55-2210-224-12
1-14. MISCELLANEOUS CONTROL DEVICES (cont)
4 ENGINE TEMPERATURE WARNING RELAY (ETWR). If temperature of the engine becomes excessive, a buzzer
will sound. If temperature continues to rise, safety circuits will cut off power to the traction motors which are powered
by the engine that is overheating.
5 TIMER. This timing device cycles the four electric drain valves. There is one valve on the bottom of each of the main
reservoir air tanks and one each on top of the main reservoir air filter and the secondary air filter. When input power
is applied to the timer, a timing cycle will cause a short and long blast of air at the drain valves every 3 minutes.
6 MOTOR KILL RELAY (MKR). Shuts down all engines in a multiple unit when the throttle is placed in the STOP
position.
7 GROUND RELAY CUTOUT SWITCH (GRCO). A single-pole, single-throw knife switch which can be opened to
disconnect the ground relay circuits.
8 GROUND RELAY (GR). The ground relay is provided to detect grounding that develops between the traction motor
power circuits and the locomotive frame. When current flows through the ground relay trip coil, it activates the relay
which locks in the energized position. This action lights the ground warning light and returns the diesel engines to
idle speed. The relay can be reset by moving the throttle to IDLE and pressing the GROUND RESET button.
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