The charging system used on HK, HT and HG Holden models was designed to keep the battery charged while supplying electrical power for the ignition system, lighting and accessories. These vehicles used either Bosch or Lucas alternator systems depending on production period and equipment, with an external voltage regulator controlling the charging output. When working correctly the system maintains stable battery voltage and reliable electrical performance, but worn components, poor wiring connections or incorrect regulator settings can quickly lead to charging problems.
Undercharged battery
• Loose fan drive belt
• Defective battery
• Voltage regulator set too low
• Loose connection in charging circuit
• Corroded electrical connections in charging circuit
• Damaged or deteriorated wiring
• Faulty generator or alternator
• Defective voltage regulator
An undercharged battery usually results in slow engine cranking, dim lights and repeated battery discharge after short periods of driving.
Overcharged battery
• Shorted battery cell
• Voltage regulator set too high
• Poor grounding between regulator and vehicle body
Overcharging can cause excessive battery heat, rapid electrolyte loss and shortened battery life.
Indicator warning light does not operate
• Burnt out indicator bulb
• Defective bulb socket
• Damaged wiring in warning light circuit
If the warning light does not illuminate when the ignition is switched on, the charging system may fail to alert the driver to a fault.
Indicator warning light remains on while driving
• Open circuit in exciter diodes
• Failure of a positive diode
• Defective voltage regulator
• Loose or slipping drive belt
• Incorrect regulator voltage setting
• Faulty generator or alternator
When the indicator light remains illuminated it usually means the charging system is not producing sufficient output.
Noisy generator or alternator operation
• Generator mounting brackets or bolts loose
• Worn or frayed drive belt
• Damaged or worn pulley
• Worn internal bearings
• Loose fan drive belt
• Loose pulley retaining nut
• Shorted or open main diodes
• Damaged stator windings
Mechanical noise from the charging system is often caused by worn bearings or loose mounting hardware and should be corrected quickly to prevent further damage.
The charging systems fitted to HK, HT and HG Holden vehicles are generally robust, but age, wiring corrosion and worn electrical components can eventually lead to charging faults. Regular inspection of drive belts, electrical connections and regulator settings can prevent many common problems.
While this guide helps identify common engine problems, the Holden workshop manuals available from Car Manuals Direct provide the original specifications, adjustment settings and repair procedures used by Holden mechanics when these vehicles were new.