How to Troubleshoot and Fix of Alternator
The most common reason for an alternator failing to charge a battery is one of them going bad. Follow the steps below to first rule out the battery and alternator and then proceed with the rest.
Step #1 – Battery Test First (check its voltage)
1. Turn off the engine and connect a voltmeter to the battery terminals.
2. A healthy battery should read between 12.2 and 12.6 volts.
3. If the reading is significantly lower, your battery may be the problem.
Step #2 – Alternator Output Test
1. Start the engine and let it idle.
2. Measure the battery voltage again. It should now be between 13.8 and 14.2 volts.
3. Increase the engine speed to about 2,000 RPM.
4. If the voltage drops or doesn’t increase, your alternator may not be charging properly.
Step #3 – Visual Inspection
1. Check the alternator belt for signs of wear, cracking, or looseness
2. Check the alternator pulley for damage or misalignment
3. Check wiring connections for corrosion or loose connections
Step #4 – Fuse Check
1. Consult your vehicle’s manual to locate the alternator fuse. Check if it’s blown and replace it if necessary.
Step #5 – Professional Diagnosis
If these tests don’t pinpoint the issue, or if you’re uncomfortable performing them, seek professional help. A mechanic can:
1. Perform more advanced diagnostic tests
2. Check for computer errors affecting the charging system
3. Inspect internal alternator components
Step #6 – Repair or Replace
Based on the diagnosis:
1. Minor issues like loose connections or a worn belt can often be repaired.
2. For internal alternator problems or if the alternator has failed, replacement is usually the best option.
3. Consider the age of your vehicle and the cost of repairs when deciding between repair and replacement.
Common Misconceptions About Alternators
bad alternator symptoms
Many car owners have misconceptions about alternators. Let’s clear up some of these misunderstandings:
Myth: Alternators charge the battery while the car is off.
This is false. The alternator only works when the engine is running. It doesn’t charge the battery when the car is off.
Myth: A dead battery always means a bad alternator.
Not necessarily. While a failing alternator can lead to a dead battery, other issues like leaving lights on or a faulty battery can also be culprits.
Myth: Alternators last forever.
Alternators have a finite lifespan. They typically last 5-8 years (or 80k-120k miles), though this can vary based on usage and vehicle type.
Myth: Jump-starting a car will fully recharge the battery.
Jump-starting only provides enough power to start the engine. The alternator then takes over to charge the battery, but this process takes time.
Myth: All alternators produce the same amount of power.
Alternators vary in their output capacity. Some high-performance vehicles or those with additional electrical accessories may require higher-output alternators.
Myth: A noisy alternator is always failing.
While noise can indicate problems, some alternator noise is normal. Excessive or unusual noise is worth investigating, but doesn’t always mean failure.
Myth: Alternators only power the battery.
Alternators actually power all of a vehicle’s electrical systems when the engine is running, not just the battery.
