BENCH REPAIRThe task to be done was to strip down a starter motor and test the individual components of the motor to make sure they still worked, then rebuild the motor to condition that it can put back on a car.
The next test is a continuity test in which you check for resistance of the commutator, as the commutator connects to the brushes this means resistance must be low or the peformance of the starter will be affected and the armature would have to be replaced. The continuity test was done to check whether the commutator segments had a circuit, and checking the resistance of the segments, if there was resistance this would affect the magnetic field that is produced and thus reduce the performance of the starter motor and the armature would have to be replaced.
The next test was to check for armature shaft runout this is done by putting the armature on some "V" blocks and using a gauge on the side read how much deflection there is whilst spinning the shaft around. If there is to much runout this could lead to poling on the pole shoes and the armature core or it could do physical damge by chipping insulation or windings or the core itself if there is to much deflection then the armature shaft needs to be replaced.
Then using the 48 Volt test light do the ground test by placing one probe on a commutator segment and the other on the armature core or shaft the light should not glow.
Next the length of the brushes was measured this is to check for wear and tear if the brushes are to short this will give bad contact onto the commutator and this would cause sparking and create resistance.Next the insulated brush holder assembly was tested for grounding the reading should come up open cicuit if it doesn't this means that the commutator and armature are not getting the full voltage from the brushes and the performance of the starter motor would be reduced this means that the brush holders would have to be replaced.
Next the starter motor solenoid was tested to check the condition of the pull in and windings, this test is done to check whether there could be resistance within the winding connections or lack of resistance caused by internal shorting this is tested by checking the amp draw if the pull in winding was shorting the magnetic field could be to strong and the pull in winding could burnout if there is to much resistance then the winding wont produce a strong enough magnetic field to to pull in the plunger in either case the solenoid would have to be replaced. Next the hold in winding was tested to make sure that it could actually hold in the plunger and checked whether the windings could have had to much or to little resistance.causing undesired operation of the plunger if there was to little resistance this could produce a very strong magnetic field and cause the plunger to stayin when it should let go if there is to much resistance the winding might not be able to hold in the plunger and the starter wont go this would mean that the solenoid would have to be replaced.
STARTER MOTOR ON CAR TESTING
The task to be done was to test starter motors on the car, checking for voltage drops, amp draw and testing the overall efficiency of the motor.
The next test is to check voltage drops along the starter circuit first testing voltage drops from the battery positive to starter solenoid input then across the solenoid and then the earth side of the circuit from starter motor body to battery negative. These tests are performed whilst the starter motor is turning over, in a perfect circuit the voltage drop across these areas would be zero however dirty contacts and corrosion can cause voltage drops across the circuit as voltage must be used to allow current to continue flowing.