December 15, 2023

Signs of a Failing Alternator and How to Repair it

alternator battery A car’s alternator is crucial for its electrical system, charging the battery and powering electrical components while the engine runs. Understanding the signs of failure can prevent being stuck. I’m hoping that this write-up will help.

Are you stalling?  Engine light on?  Check for recalls.

Alternator Causing Dim or Flickering Lights

One common symptom of a failure is dim or flickering lights. The alternator provides power to your vehicle’s lights. If it fails, the lights may appear dimmer, flicker, or fluctuate in brightness. Notice changes in dashboard, headlights, or interior lights. These changes often occur when accelerating or at idle. If lights behave erratically, it may be a clear sign.

Weak or Dead Battery

The alternator charges the battery.  If your vehicle struggles to start, or dies while driving, it’s time to suspect it. However, remember that batteries also wear out with age. It’s important to first check the battery.

Visual Inspection:

    • Check for any signs of physical damage, like cracks or bulges.

Check the Terminals:

    • Make sure the terminals are tight and secure.
    • Look for corrosion on the terminals (white or greenish residue). If present, clean with a brush and a mixture of baking soda and water.
    • Loose can cause starting problems.

Check the Voltage:

    • Use a multimeter.
    • Set the multimeter to the DC voltage setting (usually marked as DCV).
    • Connect the multimeter leads to the terminals—red to positive (+) and black to negative (−).
    • Fully charged it should read around 12.6 volts or above. A reading below 12.4 volts may indicate a charging condition issue.

Load Test:

    • A load test determines the ability to hold a charge under load.
    • This test is best performed by a professional with a load tester.
    • The tester applies a load and measures the voltage drop. If it can’t maintain a decent voltage (around 9.6 volts) under load for 10-15 seconds, it may need replacing.

Check the Charging System:

    • Start the engine.
    • With the engine running, the voltage at the battery should be around 13.7 to 14.7 volts, indicating the alternator is charging the battery.

Check for Parasitic Drains:

    • If your battery often dies overnight or during periods of non-use, a parasitic drain might be the cause.
    • Checking for parasitic drains involves using a multimeter in series with the negative battery terminal and measuring current flow with everything turned off. This step is more complex and might require a professional.

Strange Noises from the Alternator?

Unusual noises from your car’s engine area can signal alternator problems. A failing alternator can produce a grinding or whining noise. This sound arises from worn-out bearings in the alternator. Pay attention to any new or unusual sounds when your engine is running. If you hear such noises, it’s advisable to have your alternator checked by a professional.

Electrical Component Malfunctions

A failing alternator can lead to the malfunction of various electrical components. This includes issues with the stereo system, air conditioning, windshield wipers, and power windows. If these components start working inconsistently or stop functioning, it’s a potential sign of alternator issues. Since these systems depend heavily on the alternator for power, their malfunction can be a clear indicator.

Codes Related to Voltage Irregularities:

    • P0562 – “System Voltage Low”: This code is set when the powertrain control module (PCM) detects a low voltage condition. It is a common code associated with a weak or undercharged battery.
    • P0563 – “System Voltage High”: Conversely, this code can appear if there’s an overcharging situation, which can also stem from battery issues.

Codes Related to Engine Management and Ignition:

    • Misfire codes (such as P0300 – “Random/Multiple Cylinder Misfire Detected”) can sometimes be triggered by a low battery. Insufficient voltage can lead to poor spark quality, causing misfires.  See all the OBD codes here.

Transmission Codes:

    • Low battery voltage can affect transmission control modules, leading to codes related to transmission shifting or performance.

Sensor and Circuit Codes:

    • Various sensor codes can be triggered due to voltage irregularities. Sensors require a certain voltage level to operate correctly, and a low battery can cause them to send erroneous signals or no signal at all.
    • Circuit codes, like those for open or short circuits in various systems, can also be prompted by battery issues.

Body Control and Accessory Codes:

    • Systems like the ABS, airbags, or accessories (power windows, locks, etc.) might generate codes if they receive insufficient power due to a low battery.

Idle Control System Codes:

    • A low battery can affect the idle control system, leading to codes related to idle speed or performance.

Warning Lights caused by the Alternator

Many modern vehicles have a specific warning light on the dashboard for alternator issues, often labeled as “ALT” or an icon of a battery. If this light illuminates, it’s a direct indication that there’s something wrong with the alternator or charging system. Don’t ignore this warning. Immediate attention to this alert can prevent further vehicle complications.

Final Thoughts

Recognizing the signs of a failing alternator is crucial for maintaining your vehicle’s health and avoiding unexpected breakdowns. Pay attention to symptoms like dim lights, battery issues, strange noises, electrical malfunctions, and warning lights. Regularly check your alternator’s condition and seek professional assistance when needed.