Why Is My Car Battery Charger Not Working? [Problem Solved]

Car Battery Charger Not Working

For preserving and regaining the health of car batteries, you must use a charger. It stops battery deterioration, increases lifespan, ensures the engine starts right away, and provides a fallback option in an emergency. A battery charger may occasionally begin to malfunction, and there may be a number of causes for this.

Here is a detailed explanation of a car battery charger not working, leading to the battery not charging, why they stopped charging, and their solutions.

How To Know If Car Battery Charger Is Charging Battery?

Discover how to identify if an automobile battery charger is charging or not:

Automobile battery charger
Automobile battery charger
  • Check the Indicator Lights: If the “Charging” light is on, it means that your battery is getting charged.
  • Monitor Ammeter: Certain batteries come with an ammeter or a gauge that displays the charging current. If your charger works, the needle will move from zero to a higher value to show that the current flows into the battery.
  • Check the Voltage: Test the voltage of the battery using a multimeter. The voltage of a fully charged battery will be high.
  • Listen to The Cooling Sound: If the fans and other cooling mechanisms of chargers work during the charging process, the charger is working.
  • Check the Battery Temperature: Batteries tend to get hot while getting charged. Touch the battery carefully to check the temperature.

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Why My 12v Charger Won’t Recognize Car Battery?

Faulty and loose connections, low battery voltage, corrosion on terminals, accumulated dirt on terminals, and charger compatibility issues could lead to a battery not charging.

battery charger repairs
battery charger repairs

Ensure that the electrical system receives a proper supply of voltage and that the chargers are compatible with the 12V charger to recognize a car battery.

Car Battery Charger Not Working: 10 Reasons

Here are 10 reasons that you must know why a car battery charger not working:

Reasons-Car Battery Charger Not Working
Reasons-Car Battery Charger Not Working

1. Faulty Alternator:

When the car engine is running, batteries get charged by an alternator. Signs of a poor alternator are dimmed headlights, quick loss of charge, and stalling of the engine after a jump start.

2. Wiring Issues:

A damaged or loosened battery connection can reduce the electric contact between an alternator and a battery. At certain times, engine vibrations can loosen the cables and inhibit the charging process.

3. Headlights Were Left On:

Leaving car headlights on for too long can lead to a flat battery even when the engine is turned on. Certain car accessories do not shut down properly when ignition is turned off which causes abnormal draw on the battery.

4. Charger Settings:

People alter the settings of the batteries of cars and select the wrong mode of charging which affects its operations.

5. Damaged Battery:

Old or damaged batteries of cars can develop cracks, leak battery acid, or even corrode which reduces electrical connectivity and charging ability.

6. Faulty Alternator Belt:

A frayed alternator serpentine belt can slip off the alternator pulley. The belt does not keep up with the power needed by the engine, increasing the pressure on the battery.

7. Faulty ECU:

ECU (Engine Control Unit) manages the electrical system in the car which can affect the working of the charging system. Seek professional help to avoid harm to batteries.

8. External Battery Charger:

Selecting the right external battery charger and connecting it correctly is vital. Check if your car battery needs any charger for a full charge.

9. Dead Battery and Blown Fuse:

If batteries are completely discharged, the charger might not detect it. Even a blown fuse can interrupt the charging process.

10. Charger Compatibility:

An incompatible battery charger can prevent your car battery from charging properly. Make sure that the charger is compatible with battery type and voltage.

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Car Battery Charger Not Working: Repair Guide

Malfunctioning parts can harm the car battery charger of your vehicle. Follow the steps mentioned below to fix certain individual parts of a bad battery:

Car Battery Charger Not Working Repair Guide
Car Battery Charger Not Working Repair Guide

Fix the Charging Indicator, Voltage Switch, and Bridge Rectifier:

1. Open the Case of the Charger: Open the case of the charger with the help of a screwdriver and check the major components for evident damages. Broken components can stall the functioning of the charger and are not difficult to replace.

2. Check the Circuit: Use a tool like a multimeter to see how a battery charger works. Trace all the connections and measure the voltage in different parts of the circuit. The transformer is immediately connected to the primary side of the winding’s main input. Three wires come from the secondary winding, with a central tap for the 6V output.

repairing battery chargers
repairing battery chargers

3. Two of the wires are soldered to the voltage select switch that was positioned on top, while the other is connected directly to what appears to be the bridge rectifier. The switch is attached to the bridge rectifier’s other input, where the output of the switch had a positive wire directly linked to it and a negative one linked via a metal strip that served as a current shut. The problem with the charge indicator affected the output of the circuit.

4. Check the Output of the Transformer: Remove the transformer from the circuit and measure the output voltage on the complete winding as well as on the half tap. If the voltage on half winding is around 8V and close to 16 on the entire winding, there is nothing wrong with the transformer.

5. Installation of Bridge Rectifier Wing: Attach the wires directly to the pads on the rectifier. Two are soldered to one side of the switch, and one lead from the transformer is connected to one of the AC pins of the rectifier. The other 2 contacts on the switch are soldered together before being connected to the second AC connection on the diagonally opposite side of the rectifier.

The output lines are placed on the other pins, with negative wiring going first to a resettable fuse and then to the negative connection on the rectifier and the positive wire attached straight to the rectifier.

6. Bring It Together: Check the wiring of a vehicle’s components and check if every component is where it should be and if the wires are properly fastened. Close the box and either remove the corrosion or replace the alligator clips.

7. Check the output by using a voltmeter. If the reading is 8-9V for a 6V battery and 14-15 V for a 12V battery, your battery is receiving enough voltage and will start working properly.

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Check the Battery Charger Output:

8. Disconnect the battery charger to ensure that it does not emit any electricity. Connect the charger to a standard electrical outlet and activate the charger.

12v battery charger not charging
12v battery charger not charging

9. Use a voltmeter to check if the charger is generating electricity. To do so, attach the red voltmeter wire’s other end to the metal clamp at the red battery charger cable’s other end. The metal clamp at the end of the black cable from the battery charger should hold the black wire end from the voltmeter.

10. If the reading is above 12 volts on the voltmeter, the problem is with the battery and not the charger. If the reading is zero, check the fuse of the charger.

Replace Plug Fuse:

11. Take the plug out of the primary socket and remove the cover of the plug. Make sure that the three wires are tightly connected to the terminals before replacing the fuse. Loose ends of wires will not allow the charger to operate.

how to fix a battery charger
how to fix a battery charger

12. Use a screwdriver to tighten loose connections and if any of them are unplugged, release the terminal screw, insert the wire, and tighten it.

13. Fuse the plug and remove it using a flat-head screwdriver. Insert a replacement fuse into the holder for the fuse plug by using a finger to press it into the position.

14. Plug the device into the outlet and activate the charger. Take a voltmeter and check the reading. If it says that it is above 12V, the battery is working. If there is none, turn it off. To replace the fuse on the battery charger, repeat step 3.

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Replace Battery Charger Fuse:

15. The fuse on the battery charger is usually located on the front, along with other extra fuses in the same location.

Fix Car Battery Charger Not Working
Fix Car Battery Charger Not Working

16. Unscrew the cover with your fingers or gently push a screwdriver into the clip to pry it open. Remove the fuse from the fuse holder using your fingers.

17. Insert a fresh fuse into the holder and close the cover. Turn on the charger by plugging it into the wall outlet.

18. Once plugged, check the voltmeter; the battery is fixed if it registers a value above 12V. However, if the value is zero, get the wiring checked by a professional or buy a new battery.


Frequently Asked Questions about car battery charger not working.

How to fix a battery charger that won’t charge?

Check the power source, clean terminals, ensure correct connections, review settings, inspect cables, consult the manual, or seek professional help if needed.

How to troubleshoot a battery charger for car?

Check the outlets, see if the battery is in good shape, inspect the charger for any other signs of damage like corrosion or rust, and keep your charger clean to avoid any trouble.

Is it safe for me repairing battery chargers myself?

Yes, if you have determined the cause of the battery failure and if your battery does not show any visible sign of damage. However, if anything does not work properly, seek expert advice immediately.

Is it common for a 12v battery charger not charging?

It is not uncommon for a 12V battery charger to not charge due to faulty connections or charging problems. Proper troubleshooting can often resolve them.


Once you have determined that your charger is not working, ensure you get the charging system checked by a professional. Regular maintenance to maintain good condition and careful use of the charger can prevent multiple charging-related problems. Remember that safety comes first. Therefore, it is always important to consult the charger’s manual and exercise caution when working with electrical equipment.

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Originally posted 2023-12-09 14:59:14.

Why Is My Car Battery Charger Not Working? [Problem Solved]
Why Is My Car Battery Charger Not Working? [Problem Solved]

Kudrat Sandhu
Kudrat Sandhu

Kudrat is a skilled content writer at Mount Shine, specializing in assisting everyday consumers with automobile guides and choosing the best auto parts.

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