How to Test for a Faulty Car Alternator That's Not Generating Electricity?
2 Answers
Steps to test for a car alternator not generating electricity: 1. Set the multimeter knob to DC voltage 30V; 2. Connect the red probe to the alternator's "armature" terminal and the black probe to the casing; 3. Run the engine at medium speed or higher. The standard voltage for a 12V electrical system should be around 14V, while for a 24V system, it should be around 28V; 4. If the measured voltage matches the battery voltage, it indicates the alternator is not generating electricity. Reasons why a car alternator may not generate electricity: 1. Diode breakdown, failing to rectify; 2. Brushes stuck in the brush holder, preventing the alternator from being excited and thus not generating electricity; 3. No power to the rotor's field coil; 4. Phase-to-phase short circuit or grounding in the stator coil; 5. Loose rotor claw poles.
As an old hand who's worked in a repair shop for decades, dealing with a generator not producing electricity requires a steady approach. The first step is to check the fuse box for any blown fuses, as they're often the culprit. Then start the engine and use a multimeter to measure the voltage at the battery terminals. If it's below 13V at idle, it's probably a generator issue. Also, check if the drive belt is loose - if it's too loose, it won't turn properly. If all these seem normal, the problem might be worn internal brushes or faulty diodes. I recommend against casually dismantling the generator - it's easy to get shocked. After confirming the fault by measuring terminal output, it's best to take it to a professional shop. Safety first - don't mess around and risk creating sparks.
