What happens when the voltage of an alternator drops?
Voltage drops on the negative side can cause overcharging. When a new alternator is installed, check the battery voltage and use a battery charger to bring the battery up to full charge before you return the vehicle to your customer. Also, start the engine and use your DVOM to check the charging output of the alternator.
When does the alternator light turn on the battery?
On older vehicles, the battery light would turn on the alternator light when the alternator output or battery voltage dropped below a preset value. The battery light on modern vehicles, however, is controlled by data and trouble codes. This is why a scan tool is essential to diagnosing a charging system.
When to troubleshoot an unusual voltage system drop?
Troubleshooting for Unusual Voltage System Drops Usually, the first sign that your charging system is in trouble is a “battery,” “ALT,” or “CHARGE” warning light illuminating on your instrument panel while driving. It means that for some reason, the alternator has stopped charging the battery and your car is running on battery power.
What to do if your alternator is over charging the battery?
Ask an assistant to start the engine and hold engine speed at about 1500 RPM. Measure voltage across the battery with your DMM. You should get 0.5 to 2 volts higher than base voltage. If you are getting more than 2 volts above base voltage, most likely your alternator is over-charging the battery or the battery is faulty.
What causes an alternator to output low volts?
If the voltage at the battery and alternator don’t match. For example the battery reads 12v and alternator reads 14v. This means that there is an issue with wiring. While applying the same conditions as above.
On older vehicles, the battery light would turn on the alternator light when the alternator output or battery voltage dropped below a preset value. The battery light on modern vehicles, however, is controlled by data and trouble codes. This is why a scan tool is essential to diagnosing a charging system.
Troubleshooting for Unusual Voltage System Drops Usually, the first sign that your charging system is in trouble is a “battery,” “ALT,” or “CHARGE” warning light illuminating on your instrument panel while driving. It means that for some reason, the alternator has stopped charging the battery and your car is running on battery power.
Ask an assistant to start the engine and hold engine speed at about 1500 RPM. Measure voltage across the battery with your DMM. You should get 0.5 to 2 volts higher than base voltage. If you are getting more than 2 volts above base voltage, most likely your alternator is over-charging the battery or the battery is faulty.