starter off car

this assignment required me to disassemble a starter motor and test its components to check their working condition andto dismantle a starter we were given the below to follow in sequence:

1. Scribe alignment marks along the two end housings and field housings (main body) of the starter motor, this will help to align the major components.

2. Remove M terminal wire from the solenoid (this wire connects the output from the solenoid to the starter motor)

3. Scribe alignment marks on the solenoid body and mounting then remove solenoid

4. Remove any screws in the commutator end housing (failure to do this can result in major damage to the brushes or field windings).

5. Remove commutator end housing

6. Remove brushes as necessary to remove brush plate assembly

7. Remove field coil housing (main body of the starter motor).

8. Remove shift fork from drive end housing (it is important that you mark the position of the shift fork).

9. Remove the armature assembly

10. Remove the overrunning clutch from the shaft (clean any burrs with emery paper for easy removal of the clutch)
    
    

    
    

    the next test was the Armature ground test. this is done to establish whether there is a short in the insulation which,if there is, would compromise the armature's magnetic field ,reducing or impairing the performance.If this be the case the armature would need replacement. To do this,on your multimeter select the Ohms(unit of resistance) range and
    and with the multimeter probes check between each of the commutator sections and the armature core. 
    MANUFACTURE SPECIFICATION:Infinity
    TEST RESULT: 1 (on my multimeter this is equivalent)

    
    

    
    

    
    

    next is the continuity circuit test. this is testing the resistance of the commutator,which should be none or low,since it makes contact with the brushes feeding electricity to the windings. if there is high resistance this would affect the function of the armature as the motor would not turn and the starter motor would not work.the armature would have to be replaced.With the Ohmmeter in the same range check continuity between one of the commutator segments while moving the second probe around on each of the other commutator segments.

     

    MANUFACTURER SPEC    :0 - 1 Ω
    TEST RESULT: Pass
    

    
    

    
    

    Next was measuring the diameter of the commutator with Venier calipers. if the diameter was too small it would make bad contact with the brushes affecting the continuity which inturn would cause bad performance, the armature would have to be replaced.

    the mica undercut is to make sure there is enough space between segments and prevent shorting in the circuit and ensure there is good contact with the brushes.

    MANUFACTURER SPEC:26.8mm – 31mm

    TEST RESULT: 30mm.....pass
    
    
    MICA UNDERCUT SPEC:0.7mm – 1.0mm
    TEST RESULT: 0.8mm....pass
    

    
    

    
    

    the armature shaft runout test is to check how much runout there is on the armature. if there is too much runout, it would cause poling or damage to the core or winding as it spins.To check for run-out, place the armature between the “V” blocks.Turn the armature 360° while reading the dial test indicator set up on the armature core.

    MANUFACTURER SPEC:0mm – 0.2mm

    TEST RESULTS:0.03 mm.....pass
    

    
    

    
    

    
    

    the next test i performed was on the growler machince. to do this,

    1. Place the armature on the “V” of the growler.

    
    

    2. Turn the switch on to Growler position.

    
    

    3. Hold a hacksaw blade or metal strip along the armature and rotate the armature.

    
    

    if the hacksaw vibrated it indicated an internal short in the armature core.this means there is damage in windings insulation and the current is not passing through it.

    When i perfomed this test the hacksaw did not vibrate indicating no short therefore the component passed

    
    

    
    

    Next test i did was for Continuity in the Field Windings..depending on the design of the motor, the windings maybe or maynot be grounded. This particular one was not grounded  With the meter in the Ohms range, place the probes on the windings and get the reading. There shouldn't be too much resistance as this would interfere with the magnetic field and the coils would need replacement.

    MANUFACTURERS SPEC:0 – 0.02Ω

    TEST RESULT: 0
    
    
    If the windings are grounded,this particular test would not apply. In that case the black probe of the multimeter would need to be on the starter motor body and any reading would indicate a fault.
    
    
    Measure the length of the brushes and a visual inspection was next.the inspection is for wear and tear and cracks.if the brushes are too short,they would have bad contact with the commutator and this would short the circuit and drain the battery without any motion occurring.
    MANUFACTURES SPEC: 5mm(new brushes 14mm)
    TEST RESULT: average of 13.6 mm...pass
    
    
    Then i tested the grounded insulated brushes for short circuit. this required the Ohm meter set on the lowest resistance and an open circuit result should be obtained. If not, the brush holder would need replacement as this means the commutator and armature wont get enough voltage, resulting in a bad performing starter.
    INSULATED BRUSH HOLDER
    MANUFACTURERS SPEC: infinity
    TEST RESULTS: 1(equivalent of my meter)
    
    
    The nest test was that of the solenoid,to check the pull in winding.this test checks the resistance or lack of it in the winding connections.this is done with a low voltage for five seconds to prevent heat damage.to do this i connected the battery supply terminal "s" and starter motor supply in"m" to a 9v power supply(Load tester). The amp draw was within spec. and the plunger was pulled in.
    
    
    Next was the hold in test which establishes whether it can actually hold in the plunger and shows if the windings  have enough resistance,too much or too little could affect the plungers action.too much and the plunger is held in longer than its supposed to by the created magnetic field and too little it would not e enough to hold it in.
    To do this test, connected a power supply between the "s"terminal and the solenoid body.with my finger i pushed in the plunger and thenn applied the power. effectively the plunger should stay pulled in without me holding it in and it did.
    
    The final test was a visual inspection of the pinion gear, bushes and clutch. the pinion gear check was for damage and smooth movement along the armature shaft and it was good by turning the pinion gear in the direction of motor rotation, the clutch should free wheel and against direct of rotation it should lock.
    The bushes i checked for wear and tear which was very minimum and the clearance into the end housing.
    After completing this tests i was ready to assemble the motor back together.The motor should run as before disassembling or  better if repairs were needed,in my case none and it was in good working condition.