This blog is of the pre engaged starter motor I unassembled, tested and reassembled in pratical.
We were all given a start motor each to work on. First I had to do a no load test which indicated how many volts and current was passing through the starter motor. the voltage was 11.4 v and current was 59 Amps. This is telling me that theres enough pressure. Now, strip down the starter motor and test the individual components of the motor to make sure they still worked, then reassembling it again. First was to do a visual on the componets to see if any scratches chips were present. If theres visable defects then parts it would need replacing.
Then was ground circuit test positive probe on the commutator segments and common (ground)on the armature core, the reading should be infinite if there is a reading this would mean that there is short in the winding and will reduce the performance of the starter motor, and the armature core would need to be replaced.
The next test is a continuity test. I checked for resistance on 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.
Then a 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 therefore reduce the performance of the starter motor and the armature would have to be replaced.
Next the commutator diameter was measured using a micrometer if the commutator was small in diameter this wil produce a weak connection between the brushes and the commutator this would create resistance and cause sparking if this was happening then the armature would have to be replaced. Then the mica undercut was measured using the micrometer again this is to make sure that there is enough space to stop any two segments from shorting together and if the mica is not deep enough it can wear out the brushes faster.
Next test was to check for armature shaft runout i done this by putting the armature on "V" blocks and using a gauge on the side read how much deflection there is while 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 an alternative test to checking continuity of the commutator segments was done, the test applied 48 volts to the segments giving a much greater load to the windings this is done by using a 48 volt test light if everything is good the light would go on, with the same machine i did a armature ground test if the test light did not glow then the armature shaft is not grounding.
Then using a machine called the growler the the armature core was tested for internel shorting. By turning on the growler machine and spinning the armature and holding a hacksaw in over the top of the armature if the hacksaw touches while testing this will show an internal short this could affect the performance of the starter motor and the armature would need to be repalced.
The next test was to test continuity of field coils this test only counts if the field coils are not grounded, setting the multilmeter to ohm's and place the probes on each end of the winding and test the resistance of the field coils if theres to much resistance then the magnetic field would not be as strong and the starter motors performance would be reduced which then the field coils would need replacing. If the field windings are grounded then place the multimeter probe on the field wire and the black probe on the starter motor body. This checks the resistance of the field wires and for grounding if the field wires are grounded this would give a reading on the multimeter and the field wires would have to be replaced.
Next the length of the brushes were measured, this is to check for cracks and other damage if brushes are 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 so the brush holders would have to be replaced.
Next the solenoid was tested to check the condition of the pull in and windings, test is to see if there could be resistance within the winding connections or weak 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 pull in the plunger in which 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 if the windings could have had too much or little resistance. 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 may not be able to hold in the plunger and the starter wont go this also would mean the solenoid would have to be replaced.
Last test was a visual inspection on the pinion gear, bushes, and the clutch, checking the pinion gear for cracks or scratches that could mean that the pinion gear is engaging the ring gear of the flywheel in the wrong way causing damage to both the pinion gear and the ring gear, then the bushes are checked for wear and tear and see if the space between the housing and the shaft are appropiate then the one way clutch is checked for free movement and will lock up in place correctly, after this the starter motor has been fully checked and its now ready to reassemble.
When starter back together its ready for a no load test and the readings should be the about the same as they were before the starter motor was stripped this shows starter has been put back together properly and the current will flow through the circuit as it should.
No comments:
Post a Comment