In terms of fault finding guidance and advice when dealing with rotating electrics products the first most important point to remember is that the battery is the heart of the charging and starting system. Before doing any other fault diagnosis first check that the correct battery is on the vehicle and that it is in good condition.
Let us first look at starters and then we’ll move on to alternators:
Starters
Problem: Engine does not crank when ignition key is turned to “start” – starter makes no sound
■ Battery in low state of charge. Charge or replace.
■ Ignition key switch is faulty. Check. Replace if necessary.
■ Battery connections poor. Check; clean; repair.
■ Connections to starter motor are loose/broken or corroded. Check; clean; repair.
■ Possible starter motor fault. Check and replace if necessary.
Problem: Starter motor clicks when ignition key is turned to “start”, but engine does not crank or cranks slowly
■ Battery in low state of charge. Charge or replace.
■ Battery connections poor. Check; clean; repair.
■ Main cable connection to starter motor is loose/broken or corroded. Check; clean; repair.
■ Possible starter motor fault. Check and replace if necessary.
Problem: Engine cranks OK but will not start
■ Battery in low state of charge. Charge or replace.
■ Likely fuel/ignition problem – could damage starter if continually cranked.
Problem: Engine cranks OK and starts but starter motor remains in mesh
■ Ignition key switch held in “start” position. Release key.
■ Ignition key switch faulty or vehicle wiring fault. Switch off engine; check wiring system – possible starter motor fault. Check and replace if necessary.
Alternators
Problem: Ignition warning lamp does not illuminate
■ Ignition warning lamp/relay faulty
■ Battery totally flat or faulty – recharge and test
■ Ignition switch is faulty
■ Engine management fault (if alternator is ECU controlled)
■ Possible alternator fault. Check and replace if necessary.
Problem: Ignition warning lamp stays on
■ Faulty battery – charge and test.
■ Check battery connections.
■ Possible alternator fault. Check and replace if necessary.
Problem: Ignition warning lamp glows
■ Battery totally flat – recharge and test.
■ Check battery and alternator connections.
■ Additional equipment results in excessive current draw.
■ Possible alternator fault. Check and replace if necessary.
Problem: Battery goes flat
■ Parasitic load, such as broken boot light switch leaving lamp permanently on.
■ Additional equipment results in excessive current draw.
■ Possible alternator fault. Check and replace if necessary.
Technical poster for garages
Remy Automotive has recently announced the introduction of a new fault diagnosis poster which has been specifically designed to help the mechanic properly diagnose vehicle faults before fitting a new starter or alternator. These new A2-size posters are now available free to garages through their local factor.
