Starter Motor Fault Finding

The most common Lucas starter motor was fitted to all Austin Seven models from 1932 to the end of production in 1939. As the starter is not part of the routine checks carried out before taking the car out for a run its role is taken for granted, mostly overlooked until something goes wrong.

The short, dull thud or silence usually indicates that the mechanism has jammed. Moving the car forward and backwards in 3rd or 4th gear normally frees the bendix from the flywheel, otherwise put a screwdriver into the slot on the end, or a spanner on the exposed square spindle, at the back end of the casing and turn anti-clockwise.

If the problem is still not solved . . . . . .

Many of the common faults can often be found by observation. Don't blindly dismantle it into a pile of bits before you start looking for the fault. You have probably missed it already!

If the starter has failed to operate on the car do not assume that the starter is faulty, it is often the connection between the battery and the starter.

External faults to look for:

Duff battery
Corrosion betwen battery terminals and clamps
Bad connection between clamps and cables
Faulty earth connection
Loose connections

Potential starter motor faults

Contacts 1

1. Switch
Cable to switch connection
Switch contact to motor contact

Damaged flywheel

2. Starter motor - mechanical
Sticking bendix
Damaged bendix teeth
Damaged teeth on flywheel (photo)
Broken spring
Weak, broken or missing retaining clip (photo)
Worn, dry bearings
End float on armature

3. Starter motor - electrical
Brush connections
Weak or broken brush springs
Worn brushes
Field winding continuity
Armature continuity
Commutator wear
Connection between field and external switch contact (photo)

These notes were prepared by Andrew Jarmin for a Teach-in on starter motor fault finding.

See also:

Starter Motors

Starter Motor Repairs

Starter Motor Servicing

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