When you see the charging system failure light illuminate while you drive, something’s gone wrong with one of the charging system’s parts. You must immediately deal with the issue that triggers the warning light. Otherwise, if you ignore the illuminated light, you might end up stranded on the roadside with a discharged battery, waiting for a tow.
So what are the potential problems the charging system failure light warns about? And what are the parts that likely failed and need repair or replacement?
What Does the Charging System Failure Light Warn About?
Also called the check charging system light, the charging system failure light is one of the warning lights on your car’s instrument panel. A small icon depicting a car battery sets it apart from the other lights. Some failure lights feature abbreviations: “alt” for the alternator, “batt” for the battery, and “chg.” for the charging system.
If the powertrain control module (PCM) detects a problem with one of the charging system’s parts, it activates the failure light to warn you.
An illuminated charging system failure light indicates an issue with the alternator, the battery, or one of the components related to either part. Check these parts for any issues that might activate the warning light.
Inside the alternator are many moving parts that wear out over time. A faulty component will have a detrimental effect on the device’s performance. The alternator might even fail, requiring its replacement.
The alternator’s wiring might’ve also developed an issue that affects the current flow. Corroded wires can drastically reduce the charge that reaches the engine, while loose wiring and shorts can cut the current flow entirely.
Alternatively, the problem might lie with the car battery or its connectors. The PCM checks the battery state of charge (SOC), which is the remaining electricity in the cell.
In an operational charging system, the alternator raises the SOC by charging the battery while the engine runs. If you operate many power-intensive applications, the drain will reduce the charge supplied to the cell. Too much demand can exceed the alternator’s power generation capacity, forcing the battery to contribute its power reserve instead of charging.
If the SOC drops too low, the battery runs the risk of discharging. The check charging system light turns on to warn you about a potentially discharged battery.
Whenever you start your vehicle, you might notice that the charging system failure light illuminates for a few seconds before going dark. This short activation is a normal process that tests the warning light bulb.
What Should You Do If the Check Charging System Light Turns On?
First of all, stay calm. While an illuminated check charging system light indicates that the alternator isn’t working, there’s usually enough battery charge to get you through the next few miles.
Look for a spot to pull over without blocking the road for other drivers. You want to minimize the risk of getting sideswiped by accident.
Once you have parked your car and ensured your safety, check the following parts:
Alternator
The alternator is the heart of the charging system. This small generator produces electrical power in alternating current (AC). Diodes convert AC into direct current (DC) that the car’s battery can receive and store.
Older vehicles use a dynamo instead of an alternator.
Alternator Drive Belt
This drive belt connects the alternator to the engine. It powers the alternator while the engine is running.
Some vehicles rely on their serpentine belt to power the alternator instead of using a dedicated drive belt for the generator. If you own one such car, check the serpentine belt.
Like any other drive belt, the alternator drive belt deteriorates over time. A worn-out drive belt will deliver reduced or erratic performance.
The alternator drive belt can also become loose. Usually, you can fix this problem by tightening the belt. You might have to replace this part in the future.
Alternator Wiring
Wires connect the alternator and the battery. They carry current to the battery.
Look for signs of corrosion on the wiring’s metal parts. See if you can remove some of the substance without damaging the wires. You must exert care when performing this task.
Also, check the connection between the alternator and its wiring. The connectors might have gotten loose. In many cases, you can fix the issue by tightening the connection. However, old or worn-out connectors might require replacement.
Car Battery
The battery supplies the electricity required to start the engine. It also provides extra power to help the alternator meet increased electrical demands while you drive.
Check the car battery’s connectors for signs of corrosion or looseness. If you find corroded terminals, clean them as much as possible to improve the current flow. Also, tighten any loose connectors that you come across.
If the battery discharges or fails, you must replace it.
What Tests Should You Run on the Charging System?
You will need to run tests to determine what triggered the check charging system light. Here are some of the tests:
Charging Voltage Test
This test measures the charging system voltage at the battery. It requires a digital multimeter. Furthermore, the battery needs at least 75% charge for accurate results.
If your vehicle uses a computer to control its charging system, you can diagnose it with a scan tool.
Drive Belt Check
This test checks the alternator drive belt for cracks in its ribs. It also measures the belt tension using a gauge, marks on the tensioner, a torque wrench, or deflection.
AC Ripple Voltage Check
AC ripple is very high AC voltage from the alternator. It’s usually an indicator of an alternator problem. The AC ripple voltage checks look for signs of high voltage.
AC Ripple Current Check
The AC ripple current check measures how much of the alternator’s rated amperage output is AC ripple. If the percentage reaches 10% or more, replace the alternator.
Charging System Voltage Drop Testing
The alternator and battery require good connections. A voltage drop test evaluates the condition of the wiring between the alternator output terminal and the battery positive terminal.
Alternator Output Test
The alternator output test looks at the current and determines if the device generates enough amperes.
Minimum Required Alternator Output Test
This test measures the minimum electrical load the alternator must meet while operating your vehicle. If the alternator can’t produce enough current, the battery gets drained.
Rectifier Test
This test checks for rectifier-related problems. Also called does, the rectifier converts alternator-produced AC to battery-compatible DC. Issues with the diodes can lead to AC ripples that reduce the alternator’s effectiveness.
What Is the Charging System?
As its name indicates, the charging system keeps the battery charged and generates electricity for various features while the engine runs.
The charging system consists of the alternator, battery, and associated wiring. It also includes the powertrain control module (PCM) that monitors the system during operation.
For additional information about the charging system, check out this article.
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