Figure 5. Alarm System Wiring Diagram
The alarm system shown in Figure 5 is similar to the automatic electrical shut-down system, but uses a warning bell in
place of the air shut-off valve solenoid. The bell warns the engine operator if the engine coolant overheats or the oil
pressure drops below the safe operating limit.
When the engine is started and the oil pressure is sufficient to open the oil pressure switch contacts (opening pressure is
stamped on the switch cover), the alarm switch must be turned on manually to put the system in operation. The water
temperature switch is normally open. Should the engine coolant exceed 205 ° ± 5 F (96 ° ± -15 C), the water
temperature switch will close the electrical circuit and sound the alarm bell. Likewise, if the oil pressure drops below the
setting of the oil pressure switch, the switch will close and cause the bell to ring. The bell will continue to ring until the
engine operator turns the alarm switch off. The alarm switch must also be turned off before a routine stop since the
decreasing oil pressure will close the oil pressure switch and cause the bell to ring.
If the alarm bell rings during engine operation, stop the engine immediately and determine the cause of the abnormal
condition. Make the necessary corrections before starting the engine again.