Battery warning light on: causes and the faults that trigger it

1. 1. Faulty or worn alternator

   Common cause

   RACE names the alternator as the most common reason the battery does not charge: at the end of its life it stops supplying enough power. Among its internal parts, RACE cites the voltage regulator, the diodes and the bearings as the source of the fault, and Autodoc Club adds a defective regulator to the causes of code P0562 (system voltage low).^[3][4][5]

   Faults with with the alternator and starter motorP0562

2. 2. Loose, worn or broken auxiliary (alternator) belt

   Possible cause

   RACE presents it alongside the alternator as a cause of the warning light, and Autodoc Club explains that if the belt breaks, the electrical systems stop receiving power and the battery drains quickly. RACE warns that a snapped belt can damage engine components, with costs of over 1,000 euros, and Autodoc Club adds that the power steering and the water pump can also fail.^[2][4][5][6]

   Faults with with the alternator and starter motorP0562

3. 3. Loose or sulphated terminals and faulty connections

   Possible cause

   RACE lists loose terminal bolts and corroded or rusty terminals among the five causes of a battery not charging: they stop current from flowing. Autodoc Club includes loose or corroded terminals among the causes of code P0562.^[4][5]

   Faults with with the 12 V batteryP0562

4. 4. Battery at the end of its life

   Possible cause

   RACE counts a worn-out battery among the reasons it does not charge: its cells no longer store energy, something it puts at 3 to 5 years of use. In another article it speaks of an average life of around 5 years depending on use. Autodoc Club lists a weak or defective battery among the causes of code P0562.^[4][5][7]

   Faults with with the 12 V batteryP0562

5. 5. Wiring, earths or fuses in the charging circuit

   Uncommon

   Autodoc Club includes damaged charging-system wiring, blown fuses and poor earth connections among the causes of code P0562, which is usually accompanied by the battery warning light being on.^[5]

   Faults with with the electrical wiringP0562

1. Switch off non-essential electrical loads (air conditioning, radio, interior lights), find a safe place to stop and do not try to finish the journey.^[2][3]
2. If the car no longer starts, do not keep trying over and over: RACE warns that this damages the starter motor. Call breakdown assistance.^[4]
3. With the engine off, check whether the auxiliary belt is broken, loose or cracked, and whether the battery terminals are loose or rusty. A squeal or whistle from the engine is a clue to a worn belt or worn alternator bearings.^[3][4][6][8]
4. If you have a voltmeter or multimeter, measure the voltage: according to RACE, with the battery charged and the engine off it should read between 12.4 and 12.7 V, and with the engine running between 13.8 and 14.7 V if the charging system is working; Diariomotor mentions more than 13.5 or 14 V.^[8][10]
5. Look out for other alternator symptoms: dimmer dashboard lights or headlights, slow electric windows or flickering screens. If they appear, have a garage check the alternator and its belt, as they are the most frequent causes.^[3][4][8]

Urgency: As soon as possible

It is not advisable to keep driving. RACE classes the light as red and warns that the car can run out of power and stop unexpectedly; if the battery runs flat, power assistance for the steering and brakes is also lost. Autodoc Club, regarding code P0562, allows only essential driving, and only as far as the nearest garage, because of the risk of complete electrical failure. If the belt has snapped, Autodoc Club considers it unsafe and advises against driving. The sources do not say how many kilometres a car can cover with a faulty alternator.^{[1][2][3][5][6]}

1. • Medium severityFrequency: Occasional1.7 CDTIPremature alternator wearBattery or charging warning light on the dashboard when the alternator starts to fail.

   Source for the symptom in the 1.7 CDTI^[11]

1. • Medium severityFrequency: CommonOpel Astra GPremature alternator failureBattery/charging warning light on the instrument cluster and a gradual loss of voltage with the engine running.Appears at around 80,000 km

   Source for the symptom in the Opel Astra G^[12]

2. • Medium severityFrequency: OccasionalBMW Serie 5 E39Alternator failure and battery drain on the BMW 5 Series E39Charging warning light, flat battery or difficulty starting.

   Source for the symptom in the BMW Serie 5 E39^[13]

3. • Medium severityFrequency: OccasionalCitroën C6Alternator failure and battery problems on the Citroën C6Battery that goes flat or charging warning light on.

   Source for the symptom in the Citroën C6^[14]

4. • Medium severityFrequency: OccasionalFiat 500XInfotainment system faults and electronic warnings (screen, Start&Stop, alternator)The battery warning light can come on because of what is actually an alternator fault (or the other way round), which makes correct diagnosis difficult; the Start&Stop system ceasing to work is also documented.

   Source for the symptom in the Fiat 500X^[15]

5. • Medium severityFrequency: OccasionalHyundai Santa Fe IIAlternator failureThe battery goes flat or the charging warning light comes on while driving.

   Source for the symptom in the Hyundai Santa Fe II^[16]

6. • Medium severityFrequency: OccasionalNissan Almera IIAlternator failure on the Nissan Almera N16Battery warning light on, or a battery that runs flat because the alternator is not charging.

   Source for the symptom in the Nissan Almera II^[17]

7. • Medium severityFrequency: OccasionalOpel Zafira ARepeated alternator failuresBattery/charging warning light on and a drop in voltage with the engine running.Appears at around 160,000 km

   Source for the symptom in the Opel Zafira A^[18]

8. • Medium severityFrequency: OccasionalSuzuki Swift IIIAlternator failureBattery warning light on, or a battery that does not charge.

   Source for the symptom in the Suzuki Swift III^[19]

9. • Medium severityFrequency: OccasionalToyota Corolla IXThe alternator can fail and stop charging the batteryBattery warning light on, lights dimmer than normal at idle and a battery that goes flat even while driving; when cold or hot the engine may be harder to start.Appears at around 120,000 km

   Source for the symptom in the Toyota Corolla IX^[20]

10. • Medium severityFrequency: OccasionalToyota VersoAlternator and battery failure on the Toyota VersoCharging warning light or battery that goes flat; the car may not start.

    Source for the symptom in the Toyota Verso^[21]

11. • Medium severityFrequency: OccasionalToyota Yaris IPremature alternator failure, more frequent on D-4D versionsThe battery warning light may come on with the engine running, the lights dim at idle, or the car may fail to start if the battery goes completely flat.Appears at around 70,000 km

    Source for the symptom in the Toyota Yaris I^[22]

Engines

• 1.7 CDTIOpel, Vauxhall and Honda1 fault with this symptom

Cars with the affected versions

• Opel
• Toyota

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