8 Culprits Your Battery Light On but Alternator is Charging | How to Fix Battery Light On Dashboard

Have you ever been met with the dreaded battery light on your dashboard, even though your alternator seems fine? You're not alone! This video dives deep into the 7 most common reasons why your battery light stays on, even with a functioning alternator.
Understanding the Battery Light
The battery light, also known as the charging system light, works directly with the alternator and battery. It essentially indicates whether the alternator is providing enough current to charge the battery while the engine is running. Normally, it should light up briefly upon startup and then turn off once the alternator takes over. However, a persistent battery light signifies a voltage difference between the battery and alternator, pointing to potential issues.
Top Reasons for a Battery Light That Won't Turn Off
Loose or Corroded Battery Connections: Over time, battery terminals can develop corrosion or loosen, causing poor electrical connection. This voltage drop can prevent sufficient current flow and trigger the battery light. Check for loose connections and measure voltage using a multimeter.
Bad Wiring or Terminals on the Alternator: Inspect the alternator for signs of corrosion, looseness, or damage on its terminals. Ensure the wires are not burnt or broken. You can also use a multimeter to measure the alternator's voltage output while the engine is running.
Bad Battery: A weak or old battery won't hold a charge, causing the alternator to work harder. Look for signs of a swollen or cracked battery case, or a sulfuric acid odor.
Faulty Alternator Diode: The diode regulates current flow. A bad diode allows current to flow from the battery to the alternator when the engine is off, draining the battery and turning on the light. Test the diode using a multimeter in diode test mode.
Grounding Issues: Corroded or loose ground connections can cause voltage drops and illuminate the battery light. Check your engine ground connections for tightness and corrosion.
Incorrect Alternator Amperage: If you've added power-hungry accessories like loudspeakers or extra lights, your alternator might not be able to handle the increased electrical load. Consider upgrading to a higher amperage alternator.
Blown Fuses: A blown fuse in the junction box connected to the alternator's B terminal can prevent the battery from charging, triggering the light.
Broken Serpentine Belt: The serpentine belt drives the alternator. A loose, worn, or broken belt can hinder the alternator's rotation, affecting its ability to charge the battery and causing the light to turn on.
Get Your Battery Light Fixed Today!
If your battery light remains on, don't ignore it! By understanding the common causes and following the steps in this video, you can diagnose the problem and get your car back in top shape. If you have any questions, leave a comment below!
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#batterylight #alternator #chargingproblems #carrepair
Timecode:
00:00:00 - Introduction
00:00:08 - Common reasons battery light stays on
00:00:20 - Battery light and alternator function
00:00:36 - Voltage difference indication
00:00:53 - Common causes of battery light
00:01:00 - Loose or corroded battery connections
00:01:09 - Impact of loose battery connections
00:01:17 - Corroded battery terminals effect
00:01:32 - Voltage drop due to resistance
00:01:42 - Checking battery terminal connections
00:01:47 - Testing battery terminal resistance
00:02:00 - Bad wiring and alternator terminals
00:02:07 - Alternator terminal functions
00:02:17 - Alternator voltage regulation
00:02:22 - Battery warning light connection
00:02:30 - Alternator ground connection
00:02:41 - Inspect alternator terminals
00:02:47 - Signs of bad alternator connections
00:03:01 - Measuring alternator voltage output
00:03:17 - Voltage comparison test
00:03:22 - Voltage drop test
00:03:38 - Bad battery
00:03:46 - Effects of a bad battery
00:04:02 - Bad alternator diode
00:04:07 - Diode function and testing
00:04:17 - Impact of bad diode
00:04:22 - Testing alternator diode
00:04:37 - Grounding issues
00:04:41 - Checking electrical system grounds
00:04:49 - Testing ground connections
00:05:03 - Inspect engine ground connections
00:05:09 - Wrong amperage rating of alternator
00:05:14 - Electrical strain from accessories
00:05:18 - Choosing the right alternator
00:05:28 - Blown fuses
00:05:33 - Impact of blown fuses
00:05:42 - Broken serpentine belt
00:05:46 - Checking serpentine belt condition
00:05:59 - Comment and subscribe encouragement
00:06:07 - Conclusion and thanks

[@smithautomotive5029]

Great vid

[@AutocornerdPros]

Thanks

[@luisserafin7473]

Hello, I have a 2005 Mercedes Benz SL 500. My battery light has come on. Both my batteries have tested at 12 v with the engine off. I have driven the car at night with the lights on and the air conditioner on with no apparent power loss. The light will not come on until I’ve been driving several miles, then it will stay on until I stop the car. After letting the car sit for several hours and start the car again, the light will be off until I resume driving it again for a period of time. Do you have any recommendations of what I need you to check on this vehicle to determine why the light is intermittent. My thought is that if the alternator is bad, the batteries would drain and the car would stop. Aside from the light being on, I feel no loss of power or sign of battery drainage. Thank you. Any thing you can offer would be appreciated.

[@AutocornerdPros]

Did you check its relay? Also see ground connections. These could cause intermittent issues