ISC, ISCe, QSC8.3, ISL, ISLe3, ISLe4 and QSL9 Engines – Alternator Overcharging

Symptom Tree  t014

This is symptom tree t014
Cause Correction

Electronic fault codes active or high counts of inactive fault codes

Read the fault codes with an electronic service tool. Refer to Section TF in Troubleshooting and Repair Manual, ISB, QSB4.5, QSB5.9, QSB6.7, ISC, QSC8.3, ISL and QSL9 Engines, CM850 Electronic Control System, Bulletin 4021416 or Troubleshooting and Repair Manual, Electronic Control System, ISC, QSC8.3 and ISL Engines, Bulletin 3666271.


Battery cables or connections are loose, broken, or corroded (excessive resistance)

Check the battery cables and connections. Refer to Procedure 013-009.


Battery cell is damaged (open circuit)

Check the condition of the batteries. Replace the batteries, if necessary. Refer to the OEM service manual.


Voltage regulator is malfunctioning

Check the voltage regulator. Replace the voltage regulator, if necessary. Refer to the OEM service manual.


Battery isolator failed (if equipped)

Refer to boat manufacturer’s specification and wiring.


Alternator is malfunctioning

Test the alternator output. Refer to Procedure 013-001 or the OEM service manual if a non-Cummins alternator.

Last Modified:  20-Jun-2005