PIN 1904918 - Caterpillar

Illustration 1 g00717738
42-MT Starting MotorThe heavy-duty starting motors are offered in 24Vand 12V versions. The 37-MT and 41-MT are similar in operation and appearance. The significant differences between the 37-MT, 41-MT, and 42-MT starting motors are noted. A list of starting motors that are covered in this manual is located in the Specifications section.The starting motor rotates the engine flywheel. The engine will run when the engine flywheel has reached an adequate speed. The starting motor has a solenoid. Electricity will cause the solenoid to move the pinion drive toward the flywheel ring gear of the engine when the key start switch is activated on the 37-MT and 41-MT starting motors. The electrical contacts in the solenoid close the circuit between the battery and the starting motor before the pinion engages the ring gear. This will cause the starting motor to rotate. This is a positive shift starting motor. Electricity will cause the solenoid to move the pinion drive in order to engage the flywheel ring gear of the engine when the key start switch is activated on the 42-MT starting motors. The electrical contacts in the solenoid close the circuit between the battery and the starting motor. This causes the starting motor to rotate. This is a positive engagement starting motor. Damage to the armature can be caused by excessive speeds. The overrunning clutch portion of the pinion drive prevents damage to the armature when the engine begins to run. This is done by breaking the mechanical connection. The pinion will stay meshed with the ring gear however, until the key start switch is released. A return spring in the overrunning clutch returns the clutch assembly to the rest position.