Section 14-00: Battery and Charging System—Service
1993 Mustang Workshop Manual
DIAGNOSIS

Charging System Test

The Charging System Test should be performed before testing any of the individual charging system components. Its "road-map" type of layout should reduce confusion in determining "what to do next" and speed up diagnosis. The component tests will determine the type of component service to be performed.

Use Rotunda Digital Volt-Ohmmeter 007-00001 or equivalent and a test lamp to test the system. Special care should be given when using the ohmmeter near "hot" circuits. The component to be checked should be disconnected from the circuit or the battery terminals should be disconnected.

 CAUTION: Damage to the component could occur, if the circuit is allowed to remain intact.

Rotunda Charging/Starting Analyzer 059-00002 or equivalent is available for testing the charging system. Test instructions are provided with the analyzer.

NOTE: When checking generator output current with the Rotunda Analyzer at the battery cable, add 10 to 15 amps to the reading because of charge current removed for engine operation.

CHARGING SYSTEM DIAGNOSIS
ConditionPossible SourceAction
  • Battery Does Not Stay Charged—Engine Starts OK
  • Battery.
  • Test battery, replace if necessary.
 
  • Loose or worn generator belt.
 
  • Damaged or worn wiring or cables.
 
  • Generator.
  • Test and/or replace components as required.
 
  • Voltage regulator.
  • Test, replace if necessary (Refer to the appropriate generator Section in this Group).
 
  • Other vehicle electrical systems.
  • Check other systems for current draw. Service as required (Refer to the appropriate generator Section in this Group).
  • Generator Noisy
  • Loose or worn generator belt.
 
  • Bent pulley flanges.
  • Replace pulley (Refer to the appropriate generator Section in this Group).
 
  • Generator.
  • Service or replace generator (Refer to the appropriate generator Section in this Group).
  • Lamps and/or Fuses Burn Out Frequently
  • Damaged or worn wiring.
 
  • Generator/voltage regulator.
  • Test, service, replace if necessary (Refer to the appropriate generator Section in this Group).
 
  • Battery.
  • Test, replace if necessary (Refer to the appropriate generator Section in this Group).
  • Charge Indicator Lamp Flickers After Engine Starts or Comes On While Vehicle Is Being Driven
  • Loose or worn generator belt.
 
  • Generator.
  • Service or replace (Refer to the appropriate generator Section in this Group).
 
  • Field circuit ground.
 
  • Voltage regulator.
  • Test, replace if necessary (Refer to the appropriate generator Section in this Group).
 
  • Lamp circuit wiring and connector.
  • Service as required (Refer to the appropriate generator Section in this Group).
  • Charge Indicator Lamp Flickers While Vehicle Is Being Driven
  • Loose or worn generator belt.
 
  • Loose or improper wiring connections.
 
  • Generator.
  • Service or replace (Refer to the appropriate generator Section in this Group).
 
  • Voltage regulator.
  • Test, replace if necessary (Refer to the appropriate generator Section in this Group).
  • Charge Indicator Gauge Shows Discharge
  • Loose or worn generator belt.
 
  • Damaged or worn wiring (battery to generator for ground or open).
 
  • Field circuit ground.
 
  • Generator.
  • Service or replace (Refer to the appropriate generator Section in this Group).
 
  • Voltage regulator.
  • Test, replace if necessary (Refer to the appropriate generator Section in this Group).
 
  • Charge indicator gauge wiring and connections.
  • Service as required (Refer to the appropriate generator Section in this Group).
 
  • Damaged or worn gauge.
  • Replace gauge. Refer to Group 13.
 
  • Other vehicle electrical system malfunction.
  • Service as required.