Examining the commutator and brush gear

Examining the commutator and brush gear

Refer to FIG 11:5 and remove the coverband 5. Hold back each spring in turn and pull gently on the flexible connection to the brush. If the brush does not move freely remove it from its holder and polish the sides using a fine file. Mark the brushes so that they will be replaced in their original positions. If the brushes are so worn that they no longer bear onto the commutator, or the brush connector has become exposed on the running face, the brushes must be renewed.

If the commutator is blackened it should be cleaned by turning it against a petrol-moistened cloth. With the brushes and commutator overhauled hold the body of the starter motor in a vice and connect it with thick cables to a 12 volt battery. One cable should go to the starter switch terminal and the other to the body of the starter. The starter should run at high speed. If it does not, it must be dismantled for further examination and testing.

Dismantling the starter

To dismantle the starter proceed as follows:

1. Remove the coverband 5 (see FIG 11:5) and hold back the brush springs and take out the brushes.
2. Remove the starter switch by releasing the two mounting screws and lift away the switch.
3. Remove the commutator end head 16, slide off the armature assembly from the drive unit and from the pole shoes.
4. Release the engagement lever pin 6 and spring 7 from the lever operating bracket on the drive end head. Lift away the lever and withdraw the pinion assembly complete which is shown in FIG 11:5.

Servicing the brushes

Test the brush springs with a balance, the correct tension is 2.5 to 2.9 Ib. according to the wear of the brushes. Fit a new spring if the tension is low.

The life of the brushes depends on the type of service in which the vehicle is being used. In normal circumstances even when the starter is being used frequently, the brushes should last more than 18,000 miles. If the wear is found to be abnormal it will probably be found that the commutator is either damaged or excessively worn. Only Fiat replacement brushes must be used.