SPN 157 FMI 4
Volvo Penta
High DC System Voltage
High voltage alarm; ECU logs system voltage too high; possible burning smell from batteries or charger.
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Safety Warning
This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.
If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.
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Possible Causes
Overcharging battery charger, Faulty alternator regulator, Incorrect charger voltage setting (12/24 V mismatch), Poor battery connection causing regulator mis-sensing
How to Fix / Troubleshooting
Safety: Overcharging can cause batteries to vent explosive gas. Ventilate the area and avoid sparks or open flames.
- Check charger settings: Verify the standby battery charger is configured for the correct system voltage (12 V or 24 V) and battery type. Adjust settings per manufacturer instructions.
- Measure charging voltage: With the engine off and charger on, measure battery voltage. If above 14.4 V (12 V) or 28.8 V (24 V) for extended periods, the charger may be faulty and should be replaced.
- Test alternator output: With the engine running and charger off, measure voltage. If it exceeds spec, the alternator regulator is likely defective. Replace the alternator or regulator assembly with a Volvo Penta-approved part.
- Inspect battery connections: Loose or corroded sense wires can cause overcharging. Clean and tighten all small-gauge sense leads on the batteries and alternator.
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Repair Difficulty
Medium
3/5
Required Part
Battery Charger
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