Starter Motors and Control Circuits Part 2
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Counter Electromotive Force is:
Voltage produced by the armature spinning in a magnetic field.
The slower the an armature rotates:
The more current it draws.
If a load on a series motor is suddenly removed:
its speed keeps increasing until it self-destructs.
To change the direction of rotation on a parallel motor, you must reverse: (2 answers)
the direction of current flow in the armature.
the direction of current flow in the field windings
While testing a starter armature, if u place one ohmmeter lead on the commutator bars and the other lead on the armature shaft and the ohmmeter reading is infinite, the armature:
is testing normal
If you are testing an armature using a Growler and the metal strip held above the armature windings begins to vibrate, the armature:
Scoring or rub marks on the laminated iron core of the armature can be caused by: (3 answers)
- a bent armature shaft
- loose field pole shoes
- worn bearings or bushings
How to check a one-way clutch ? (direction)
Hold the starter drive in one hand while rotating the drive gear in both directions
In one direction - it should hold and not slip; in the other direction, it should turn with some resistance.
What causes burning of the commutator bars ?
loose connections or poor connections - can also cause arcing of the commutator bars.
What causes an "Open" Armature Winding ?
Opens are causes by excessively long cranking times.
Check for hard starting problems that may have contributed to this failure.
If the commutator bars are black or the windings are discoloured where they are connected to the commutator you should ?
replace the armature.
How are "Short-Circuits" located in the Armature ?
are located by rotating the armature in a Growler (armature tester) w/ a steel strip such as a hacksaw blade held on the armature.
Steel strip vibrates as the shorted circuit passes below the steel strip.
How are grounds check on an armature ?
checked with Ohmmeter
place one lead on the commutator bars and the other on the armature shaft.
How do "Grounds" occur on the armature ?
Grounds occur as a result of insulation failure
which may hav been brought on by overheating of the cranking motor.
Never use _________ to clean the commutator.
First step in any starter removal procedure is to remove the:
negative battery cable first.
Field Coil tests can checked for ________ and _______ by using an _________.
Grounds, Opens, Ohmmeter.
When checking for Ground on Field Coils, where are the leads connected ?
Connect one lead of the ohmmeter to the field frame and the other lead to the field connector.
if the ohmmeter reads "infinity", the field coils are NOT grounded.
How do you test for "Opens" on field coils ?
Connect the ohmmeter leads to each end of the field coils, if the reading is open (infinity) the field coils hav an "Open" circuit and must be replaced.
How do you test for "Shorts" on field coils ?
Due to low resistance of field coils, there is no test for 'shorts'
Relays can be tested for:
proper resistance across the solenoid coil and a voltage drop not exceeding 0.2 volts across the contacts.
What can cause a no-crank condition ? (3 answers)
- open neutral safety switch
- open clutch switch
- activated anti-theft system
A starter motor current draw test measures the __________.
actual current flow required to crank over the engine
make sure to disable the ignition system (or fuel system)
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