Alternator over charging

[Solgear]

2003 GX470 with 180K miles. I've shopped around several forums and can not find the next best step to try and figure out why my alternator is charging up to 16.9 volts. The battery light came on and I drove my vehicle home hoping the alternator wouldn't die and leave me stranded. Once home, we see the alternator is producing up to 16.9 volts. So I buy a reman from Rock Auto and put it in. Battery light still on. Replace the battery, nothing changes. I have my old battery tested (was new in 2021) and its good and they take a return on the battery I just bought. So I buy another alternator thinking I was unlucky with the reman and the regulator was bad. New alternator has the same issue, although the alternator seemed to work fine for a week despite the battery light still on, and now its hitting about 16.7 volts intermittently again and battery light going on and off. All connections are fine, not corroded. Even jumped a wire from the alternator to the battery to make sure there wasn't a bad wire. Ground wires are solid. All the fuses appear fine.

There must be some kind of sensor telling my alternator to charge more. Any help is appreciated.

[RX400h]

Quote

1. Flickering Dashboard Lights or Headlights:

   • When the alternator overcharges, it can cause the headlights or dashboard lights to flicker. The excessive voltage coming through the system leads to this phenomenon.
   • However, this symptom alone doesn’t pinpoint whether the alternator is producing too much or too little charge. We need to consider other signs as well.

2. Brighter Lights Than Usual:

   • An overcharging alternator makes the lights in your vehicle significantly brighter than usual. This effect applies to headlights, taillights, dashboard lights, and any other illuminated components.
   • Conversely, if the alternator were underperforming, you’d notice overall dimmer lights.

3. Dashboard Warning Lights:

   • If your car’s alternator is overcharging, you’ll likely see a battery light on your dashboard. Sometimes, the check engine light may also illuminate.
   • Modern vehicles equipped with an OBD-II system might display a charging system code (such as P2504 – Charging System Voltage High).
   • Keep in mind that this code could indicate issues beyond just the alternator, such as voltage regulator problems, battery corrosion, or electrical shorts¹.

Now, let’s explore potential causes and solutions:

• Voltage Regulator Issues:

  • The voltage regulator is directly responsible for controlling the alternator’s voltage output. A faulty regulator can lead to overcharging.
  • Consider checking the voltage regulator’s functionality or replacing it if needed.

• Wiring Problems:

  • Damaged alternator wiring or bad grounds can affect the charging system.
  • Inspect all connections, including ground wires, to ensure they’re solid and free from corrosion.

• Battery Sensor or ECM Trouble:

  • Sometimes, an issue with the battery sensor or the car’s electronic control module (ECM) can cause overcharging.
  • Verify the health of the battery sensor and ECM.

• Professional Diagnosis:

  • Given your thorough troubleshooting efforts, it might be best to consult a professional mechanic or an auto electrician.
  • They can perform more advanced tests, such as checking the alternator’s output and diagnosing any underlying issues.