How to Check if the Generator is Not Generating Electricity?
2 Answers
Here are the relevant methods to determine if a car generator is not generating electricity: 1. Use a voltage meter for detection: When the car is running, set the multimeter knob to the DC voltage 30V range at the battery terminal. Connect the red probe to the generator's "armature" terminal and the black probe to the casing. Run the engine at medium speed or higher. The standard voltage for a 12V electrical system should be around 14V, and for a 24V electrical system, it should be around 28V. For small cars, the measured voltage is generally above 13.8V, often reaching over 14V. If the generator is not generating electricity, the voltage will drop significantly after the car is started, often falling below 12V. If the measured voltage is the same as the battery voltage, it indicates that the generator is not generating electricity. 2. External ammeter detection: If there is no ammeter on the car dashboard, an external DC ammeter can be used for detection. First, disconnect the wire from the generator's "armature" terminal, then connect the positive terminal of a DC ammeter (with a range of about 20A) to the generator's "armature" and the negative wire to the disconnected terminal mentioned above. When the engine is running at medium speed or higher, if the ammeter shows a charging indication of 3A~5A, it means the generator is working normally; otherwise, the generator is not generating electricity.
When checking if the alternator isn't generating electricity, I usually start with simple methods. First, I start the car and check if the battery warning light on the dashboard is lit. If it is, I turn off the engine and restart it to try again. If the light remains on, it generally indicates the alternator might not be working. At this point, I take out a multimeter to measure the battery voltage. With the key in the ON position but the engine not running, the voltage should be around 12 volts. If the voltage doesn't exceed 13 volts after starting, the alternator might be faulty. Next, I listen for any chirping sounds from the alternator; if present, it suggests the belt or internal components are damaged. If after all these checks the alternator still isn't generating electricity, I quickly find a reliable repair shop because a faulty alternator not only drains the battery but also affects driving safety—dimming lights can be unsettling. During regular maintenance, I also ask the mechanic to test the charging system as a precaution to avoid issues on long trips.
