PLATE 7E0317 - Caterpillar

Illustration 1 g01114061
Components for the electrical starting system
(1) Terminal box
(2) Magnetic switches
(3) Circuit breaker for the start command from the Electronic Control Module (ECM)
(4) Starting motor solenoids
(5) Starting motors When the ECM in terminal box (1) receives an input for start-up, the ECM supplies +Battery voltage to two magnetic switches (2). The magnetic switches are located in a power distribution box on the side of the engine. The start command from the ECM is protected by circuit breaker (3).The two magnetic switches are connected in a secondary electrical circuit to two starting motor solenoids (4). The start command closes the contacts of the magnetic switches in order to complete the secondary electrical circuit. This energizes the starting motor solenoids.The energizing of the starting motor solenoids causes the starting motors' pinions to engage with the flywheel ring gear.The starting motor solenoids are also connected in another electrical circuit between the starting motors and a source of +24 VDC for cranking the starting motors. After the starting motor's pinions are engaged with the flywheel ring gear, the starting motor solenoids' contacts complete the other electrical circuit for cranking of the starting motors.The starting motors crank the engine until the ECM detects the crank terminate speed. Then, the ECM removes the +Battery voltage from the magnetic switches. The contacts of the magnetic switches open and the +Battery voltage is removed from the starting motor solenoids. The starting motor solenoids' contacts open and the +24 VDC for cranking is removed from the starting motors. The starting motors' pinions are disengaged from the flywheel ring gear.Illustration 2 is a schematic of the electrical starting circuit.
Illustration 2 g01114064
Schematic for the electrical starting circuit