When the ignition is turned on, voltage is supplied to terminal 15. But the generator is not working yet, so the de-energized contact D+ acts as a "minus". The control lamp lights up, because there is a difference between the voltage of the on-board network, which receives power from the battery, and the voltage of the generator, which is still not working.
When the engine starts and the generator reaches the charging speed, the voltage regulator connects the generator to the on-board electrical equipment. Now the positive current comes from terminal 15 and additionally from terminal D+. Due to this, there is no longer a difference in voltage, the charging indicator light goes out.
When the ignition is turned on, the illuminated indicator lamp should "pre-excite" the alternator. This is the only way it can supply current even at low speeds. Although pre-excite is only necessary when starting the alternator.
Charging does not always occur
The fact that the indicator light goes out does not prove that the battery is being charged by the alternator. It only means that there is no longer a voltage difference between the battery and the alternator. If, for example, all electrical consumers are switched on when the engine is idling, the charging indicator light does not come on, although more electrical energy is being taken from the battery than a weaker alternator can provide: nevertheless, there is no difference in voltage with the battery.
[Article posted on Internet portal Opelbook.ru]
Tip: You may have noticed that sometimes the charge indicator light stays on if you start a warm engine without applying gas and it continues to idle at low speed. In this case, the pre-excitation of the alternator is too weak, it does not yet supply current. As soon as you tap the gas pedal, the red light goes out. This is normal and does not indicate a malfunction.
Visitor comments