The dashboard has many warning lights that activate when something goes wrong with their associated part. Newer vehicles have instrument cluster computers with fancy little screens that can show icons and words rather than simply turning on a warning light.
One such indicator advises you to inspect the vehicle’s charging system for issues immediately. If you ignore the warning for too long, you might find yourself stranded in the middle of nowhere because the car battery ran out of juice.
But what can trigger the check battery charging system warning? Find out what parts need a check-up when this particular warning light turns on.
The service battery charging system indicator warns that the car battery isn’t receiving enough charge to replenish it.
About 90% of the time, the battery light or warning message about the charging system is an issue with the alternator itself. The other 10% of the time it’ll be a wiring problem that is preventing the alternator from charging.
About 90% of the time, the battery light or warning message about the charging system is an issue with the alternator itself. The other 10% of the time it’ll be a wiring problem that is preventing the alternator from charging.
– Richard McCuistian, ASE Certified Master Automobile Technician
The powertrain control module (PCM) monitors the state of the battery charging system on vehicles where the PCM controls the alternator. If the PCM/ECM detects an issue with the charging system, it will turn on the check charging system warning light.
This warning is basically giving you the same information you’ll get from a plain old battery light on a vehicle that doesn’t have a message center.
Here are the most common causes responsible for turning on the service battery charging system light:
A faulty alternator is one of the most likely reasons for the service battery charging system light illuminating. Driven by the engine crankshaft through a drive belt, the alternator generates electricity. It charges the car battery, replenishing the energy storage device.
Like any other part, the alternator is subject to wear, gradually reducing its performance.
The most wear prone component in an alternator would be the brushes that slide on the rotor’s contact rings. Second would be the diodes in the rectifier and the stator winding. The least prone to fail part of the alternator electrically would be the rotor windings. The bearings seldom fail on an alternator because they’re sealed and will usually outlast the electrical components.
A faulty drive belt is another common culprit that sets off the service battery charging system warning. The belt connects the crankshaft to the alternator. As long as the engine runs, the drive belt drives the alternator, generating power for the battery and other electrical parts.
Eventually, the drive belt wears out, loosens, or fails. If the belt develops an issue, the alternator also gets affected. A faulty drive belt might diminish the alternator’s power generation, affecting the battery’s charging.
As an aside, the alternator is driven by the smallest pulley because the alternator needs to spin fast to keep the battery charged.
The A/C and power steering pulleys are larger because they need more power than speed.
The belt can wear to the point that it slips, but the alternator will continue to charge as long as the belt is tight enough. With spring-loaded belt tensioners, the belt won’t usually be the cause of an alternator warning light unless it completely comes off or the tensioner fails catastrophically.
While the illuminated service battery charging system light could trigger due to a bad battery, in most cases, it won’t. Typically, even if the battery is bad, it won’t turn on the warning light, even if the battery is too dead to start the engine.
The battery’s performance declines over the years. A battery’s cold cranking amps (CCA) will decline with use until there aren’t enough CCA for the battery to operate the starter, which is the most intense job the battery has.
An intricate network of wiring connects electrical parts. The wires transmit power and signals between the interconnected parts, ensuring smooth operation.
Unfortunately, the electrical wires and their connectors are vulnerable to corrosion. They also wear out from use and might degrade faster. If wiring issues disrupt the battery charging process, the PCM will activate the service battery charging system warning light.
Aside from the alternator, several electrical components help charge the battery. If these parts develop problems, they can set off the check battery charging system warning light.
Two examples are the voltage regulator and the battery temperature sensor. Newer vehicles also have a current sensor around one of the battery cables.
The voltage regulator controls the voltage of the alternator’s current by duty cycling the current delivered to the spinning rotor. The more current delivered to the rotor, the stronger its magnetism and the more the alternator charges.
Meanwhile, the battery temperature sensor provides readings that the PCM uses to adjust the current voltage for efficient charging. Both parts play critical roles in the battery charging system.
A bad powertrain control module might activate warning lights like the check battery charging system light, even though there’s no problem.
With the right tools and DIY car repair experience, you can identify the bad part that triggered the check charging system warning. Here are some recommendations:
Measure the alternator’s output voltage with a multimeter while running the engine. The readings must show a voltage in the manufacturer-recommended range. A bad alternator has an output voltage below or above that range.
Look for cracks, looseness, and signs of excessive wear on the drive belt. A worn-out or severely damaged drive belt will require replacement.
Furthermore, adjust the drive belt’s tension according to the manufacturer’s recommendations. A properly tightened belt will deliver the best performance.
After checking the alternator, you can measure the battery strength with the multimeter. Change the tool’s setting from AC to DC before connecting it to the battery terminal.
If the readings show a weak battery or an inability to stay charged, replace the battery. Choose a replacement that meets your vehicle’s manufacturer-recommended specifications.
Go over the battery’s cables and terminals. Remove all corrosion before tightening the battery clamps around the terminals. Clean and tight connections will ensure a steady current.
Next, check the alternator’s internal connections and wirings. Pay sharp attention to the fusible links. If you find a burned link, see if you can repair them. Otherwise, you need to replace the part.
Inspect the voltage regulator, battery temperature sensor, and other electrical parts for issues. Replace any damaged or worn-out parts.
Use an OBD-II scanner to check the PCM for issues. The computer routinely checks itself and should log the relevant OBD trouble codes. You might have to replace the module.
Some issues might prove beyond your DIY skills. Are you unable to determine what causes the service battery charging system warning light to illuminate? Contact a qualified mechanic for assistance. They have the training and equipment to identify what’s causing the problem.
Any information provided on this Website is for informational purposes only and is not intended to replace consultation with a professional mechanic. The accuracy and timeliness of the information may change from the time of publication.