- the battery is faulty;
- open electrical circuit between the ignition switch (lock), traction relay, battery and starter;
- traction relay is faulty;
- mechanical or electrical defect of the starter.
To check the battery, turn on the headlights. If the light dims after a few seconds, the battery is discharged. Recharge or replace the battery. If the headlights do not dim, turn on starter and watch the light. If their light dims, then it is faulty starter. If the headlights continue to burn brightly (and there is no click of the starter traction relay), the electrical circuit is damaged or the traction relay is faulty. If the starter rotor rotates slowly and the battery is in good condition and charged, then, starter faulty or there is a break in the starter electrical circuit.
To detect damage in the electrical circuit, disconnect the battery and clean all connections and contacts in the starter power circuit. Reconnect the battery and use a voltmeter to check the voltage across the electrical circuit elements up to the starter.
If the battery is OK and the electrical circuit is not damaged, remove the power wire from the traction relay and connect a voltmeter to it. Turn the ignition key to the "Engine Start" position. In this case, the voltmeter should show the battery voltage.
The contacts of the traction relay can be checked by connecting a voltmeter between the contact of the traction relay connected to the starter and the "ground". When turning the key to the "Engine Start" position, the voltmeter should show voltage. If there is no voltage, the traction relay is faulty or its contacts are burnt.
If the electrical circuit and traction relay are in good condition, then the fault is starter.