Off car starter testing

Testing

1. Armature

Test the armature by connecting the multimeter (on the ohm setting) between the commutator (Where the brushes run on). This should give the resistance of the coils/field windings inside the armature. Check the reading against the specifications given. To test if there is a short circuit between the coils and the body of the armature connect the multimeter's negative to the body and the positive to the commutator, the reading should be infinity. If it does give a ohm reading it means that there is a shortage inside the armature.

     2. Field coils

The field coils are tested in a similar way as the armature's coils. Set the multimeter to ohms and connect it to the terminals of the field windings, check the readings against the specifications. A short circuit can also be checked by connecting on of the multimeter's wires on the coil terminals and the other on the body of the starter, the reading should show infinity. If not it means there is a short. Some starters have fixed magnets instead of field coils. The disadvantage is that the magnets can become demagnetized, the coils are more durable.

 Starter with permanent magnets

     3. Brushes

The brushes should be measured using a vernier caliper. The reading should at least be bigger than the minimum specified value, if not then they need replacing. Another thing that needs to be checked is the commutator that brushes runs on. If it is burned black it needs to be cleaned using a fine grade sand paper. If the surface of the commutator is damaged it will need to be skimmed using a lathe or be replaced.

Commutator end bracket

    4. Solenoid

To test the terminals inside the solenoid connect the multimeter to the two terminals on the outside of the solenoid using the ohm setting. Push the plunger fully in if there is no reading on the multimeter it means that the terminals are not being connected and will need servicing. To test if the solenoid works connect the negative wire from a power supply to the body of the solenoid and a positive wire to the terminal on the solenoid that connects to the ignition. The plunger should be pulled back by the solenoid if not it means that it is faulty

Testing solenoid terminals

    5. Clutch and bearings

The pinion should move freely in one direction and move with the motor in another direction. The clutch is not working if the gear turns with the motor or freely in both directions. To check the bearing you can rotate them with your fingers if they move smoothly they are fine. The bearings should also be checked for any oil leaks and any damage.

Clutch and pinion gear