This is for the car owner who wishes to maintain his vehicle and learn more about starter motors repairs to reduce running and maintenance cost .
The starter motor is equipped with a solenoid actuated pre-engaging starter drive and over-running clutch assembly. The starter motor is a 12 volt series wound, four pole, four brush unit. The solenoid is attached to the starter drive end bracket, the solenoid plunger is connected to over-running clutch and drive pinion assembly through a link, lever and pivot pin arrangement.
When the solenoid winding are energised, the plunger acting on the lever and pivot engages the drive pinion with the flywheel ring gear and at the same time closes the switch supplying power from the positive lead of the battery to the starter motor field coils and the armature to operate the motor. As the engine fires the over-running clutch of the drive pinion assembly prevents high speed rotation of, and possible damage to, the starter armature if the solenoid winding are not immediately de-energised by releasing the switch key. The starter solenoid switch winding are energised by the key operated combination ignition and starter switch.
Starter Motors Inspection And Repairs
If the motor rotates but fails to start the engine the pinion assembly will be found to be worn. The motor fails to rotate, connect a votl-meter and you try to rotate the starter motor, if the volt-meter indicate 6 volts, the inference is hat though the current is passing through the motor winding but that the armature will not rotate. For both this conditions you need remove starter. If the voltmeter shows constant 12 volts when an attempt is made to start the motor,check whether the lead from the battery to the motor is damaged or disconnected verify the connection. And if the motor is sluggish or only rotates at slow speed the cause may loose connections in the starter motor.
Starter Motor Components.
The most important components starter motor are: Drive end bracket is in the front of the starter, Engaging lever, Pinion and engaging clutch, Solenoid, Yoke, Armature and commutator they build together, Brush holder,springs and brushs, Commutator end cover is the back of the starter.
You must disconnect the battery terminals and disconnect the battery lead from the starter motor solenoid, the switch wire must be removed from solenoid.Remove the mounting bolt after that remove the starter motor from you car engine.The installation is reversal of the removal procedure.
Dismantling The Starter Motors.
If you are looking to dismantle the starter motor you start from the back to front of the starter motor. Remove the cover commutator while lifting the brush springs, slide the brushes from their holders. Screw out the two screws witch hold the solenoid and unhook the engaging lever from solenoid and the pinion clutch assembly.Remove the drive end bracket and slide out the armature from the yoke (casing).
The Starter Motors Components Replacement
Is flexible leads are soldered to terminal lugs, two leads are connected to the brush-holder and two to the free ends of the series field coils. Unsolder these flexible leads and solder theme to the new brushes.
If the armature conductors are higher than the commutator ends, the cause will be excessive speed of the motor. The armature rubs against the pole shoes this is due to worn bearing or damage armature shaft, if the armature is damage it must be replaced. The armature shaft is carried on two bronze bushes one at each end. If the are worn to such en extent that they allow the armature shaft excessive end play they must be replaced.
The commutator in good working order it will be found to be bright, no stains, scratches or burned patches. If the commutator show serious signs of wear, mount it on a lathe , rotate at high speed and skim it up with very sharp tool, take care not to remove more metal than absolutely necessary then finish it of with fine glass paper.
Inspect the continuity of the coil and make sure that there no breaks, you can use 12 volt tester and battery connected between the insulated contact switch on the casing and each brush.
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