ALTERNATOR TROUBLE SHOOTING

Problem:

No battery light when key is in ‘ign’ position

Possible Causes:

1. Remove battery warning light wire from alternator and earth the wire. The battery light should come on on the dashboard. If not, the bulb has blown or there is a wiring fault.
2. Check engine earth and alternator earth if fitted

Problem:

Battery light stays on

Possible Causes:

1. Ensure wiring to alternator is correct. (Note : ensure that battery warning light wire has been connected to correct terminal and not an earth or phase terminal)
2. Check that the positive feed is at least 12 volts
3. Ensure that the fanbelt is correctly tensioned. If the belt has been loose, there will be black fanbelt dust around the front of the alternator
4. Some alternator charging circuits now have a charge relay and this may be faulty

Problem:

Alternator is not charging

Possible Causes:

1. Check all the above
2. If the alternator has been fitted a while, also check that :-
• The alternator has not been contaminated with oil, water etc…
• All connections are tight. Remove wiring plug if fitted and check state of terminals. If terminals are discoloured or burnt, the plug has been loose

Problem:

Alternator is noisy

Possible Causes:

1. If there is a high pitched whine, the fanbelt may be slipping. To check, spray some penetrating oil on the pulley, if the noise goes away, then the belt is loose. Advise replace belt and check state of pulley
2. If a clutch type pulley is fitted, as on the latest alternators, this may be faulty
3. Ensure that the alternator has not worked loose, particularly on diesel applications
4. Ensure that fan and pulley have been correctly fitted and not worked loose if the unit was supplied without a fan and pulley

Note :

When fitting an alternator, the battery must be fully charged otherwise the alternator may overload and blow the rectifier inside.

Care must be taken if boost charging as this can also blow the alternator, particularly if the wiring has not been correctly connected.

STARTER MOTOR TROUBLE SHOOTING

Problem:

Noisy in operation

Possible Causes:

• Check condition of ring gear
• If starter is open ended, check bush in bell-housing
• If fitted with dowel, check that it is correctly located
• Ensure starter is fitted ‘square on’
• Ensure that the starter has not worked loose, especially on diesel applications

Problem:

No operation

Possible Causes:

• Ensure exciter wire from ignition switch is fitted to correct terminal
• Check state of battery
• Ensure main feed is ok
• Check engine earth
• Check starter relay if fitted
• Check ignition switch
• If starter has been fitted for a while ensure that
• Armature shaft is not contaminated with clutch dust
• Pinion is not damaged due to ring gear or ignition switch fault
• Starter has not been overloaded. This can be confirmed by armature shaft turning blue and by shaking the starter and seeing if it rattles

Problem:

Intermittent operation

Possible Causes:

• Check all the above

A quick test:

As a final test, the starter can be checked off the vehicle by placing in a vice. Using a battery and jump leads, connect the battery earth to starter body and the battery positive to large stud (without the link wire) on the solenoid. Then using an insulated screwdriver, bridge the main feed to the solenoid exciter terminal. The pinion should throw forwards and the starter should turn.

NOTE : THIS TEST SHOULD BE CARRIED OUT WITH GREAT CARE!