31750-ZW2-F01 Honda SEE PART DETAILS - PRI; RECTIFIER ASSY., REGULATOR (12A)

Illustration 1 g00292316
Typical cross section of a solenoid
A solenoid is an electromagnetic switch that performs two basic functions:
The solenoid closes the high current circuit for the starting motor with a low current start switch circuit.
The solenoid engages the pinion for the starting motor with the ring gear.The solenoid has windings (one set or two sets) around a hollow cylinder or a hollow housing. A plunger that is spring loaded is located within the solenoid housing. The plunger can move forward and backward. When the start switch is closed and electricity is sent through the windings, a magnetic field is created. The magnetic field pulls the plunger forward in the solenoid housing. This moves the shift lever for the pinion drive gear to engage with the ring gear. The front end of the plunger then makes contact across the battery and across the motor terminals of the solenoid. The starting motor then begins to turn the flywheel of the engine.When the start switch is opened, current no longer flows through the windings. The spring now returns the plunger to the original position. At the same time, the spring moves the pinion gear away from the flywheel.When two sets of windings in the solenoid are used, the windings are called the hold-in winding and the pull-in winding. Both of the windings wind around the cylinder for an equal amount of times. The pull-in winding uses a wire with a larger diameter to produce a stronger magnetic field. When the start switch is closed, part of the current flows from the battery through the hold-in winding. The remainder of the current flows through the pull-in windings, to the motor terminal, and then to the ground. When the solenoid is activated, the current is shut off through the pull-in windings. Only the smaller hold-in windings are in operation for the extended period of time that is necessary for the engine to be started. The solenoid will now take a smaller amount of current from the battery. Heat that is created by the solenoid will be kept at an acceptable level.Starting Motor
Illustration 2 g03883275
Typical cross section of a starting motor
(1) Field
(2) Solenoid
(3) Clutch
(4) Pinion
(5) Commutator
(6) Brush assembly
(7) ArmatureThe starting motor rotates the engine flywheel at a rate that is fast enough to start the engine.The starting motor has a solenoid. When the start switch is activated, the solenoid will move the starter pinion to engage the pinion and the ring gear on the engine flywheel. The starting motor pinion and the ring gear will engage before the circuit between the battery and the starting motor is closed by the electric contacts in the solenoid. When the circuit between the battery and the starting motor is complete, the pinion will rotate the engine flywheel. A clutch provides protection for the starting motor so that the engine cannot turn the starting motor too fast. When the switch is released, the starter pinion will move away from the ring gear.Starting Motor Protection
The starting motor is protected from damage in two ways:
The starting motor is protected from engagement with the flywheel while the engine is running. The control feature will not allow the starting motor to engage if the engine speed is above 0 rpm.
The starting motor is protected from continued operation when holding the key in the "start" position after the engine starts. The Electronic Control Module (ECM) automatically disengages the starting motor solenoid when engine speed reaches 400 rpm.
Dynamic Starter Cooldown Time Multiplier is used to set the cooldown duration for the starter between cranks based on the total time the starter is engaged. For example, if the starter engagement time is set to 30 seconds and the Dynamic Starter Cooldown Multiplier is set to 4, the starter will crank for 30 seconds, and rest for 2 minutes (30 X 4 = 120).