- multimeter (in voltmeter mode with a measurement limit of 15-20 V);
- technical stethoscope.
Execution sequence
1. We prepare the car for work («Preparing the car for maintenance and repair»).
2. We start the engine. If the battery charge warning lamp lights up on the instrument panel, check:
- +12 V voltage supply to the excitation winding of the generator when the ignition is turned on (terminal L of the alternator connector);
- alternator drive belt tension.
Recommendation. Weak alternator drive belt tension («Alternator Drive Belt - Condition Check») leads to its slippage on the pulleys, which does not allow the generator to develop the necessary power and leads to rapid belt wear. Indirectly, belt slippage can be determined by the dim glow of the headlights at night and by the whistling sound in the front of the engine when the crankshaft speed increases.
3. We warm up the engine to operating temperature (not less than 80°С).
4. We turn on all the powerful consumers of the car's electricity (heated rear window, electric heater fan, high beam headlights, heated seats).
Comment. We carry out the rest of the work with an assistant.
5. By pressing the gas pedal and controlling the operation of the engine using the tachometer, we keep the engine crankshaft speed within 3000-3500 rpm.
6. We measure the voltage at the battery terminals with a voltmeter. With a working generator, the voltmeter should show a voltage of at least 14 V.
Comment. If the voltage is less, the alternator drive belt may be loose (see above), the generator circuit is faulty, the generator voltage regulator is faulty, the brushes in the generator are oily or worn out, or the generator itself is faulty (troubleshooting the voltage regulator and other parts of the generator, see the relevant sections below).
7. We turn off all consumers of electricity, while the voltmeter should show a voltage not higher than 15.1 V.
Comment. If the voltage is higher, the voltage regulator is most likely defective.
8. With a stethoscope, we evaluate the condition of the generator bearings by noise. A strong hum indicates wear on the bearing or bearings (most often the front bearing fails).