Why Does a Car Generator Fail?

[Barros]

Car generator failure can be attributed to the following reasons: Generator's own issues: It's possible that the generator itself (due to quality issues) causes burnout, leading to short circuits or burnout in other circuits, which will definitely affect the battery as well, such as charging and power supply issues. Regulator issues: Voltage fluctuations caused by internal components like the regulator can lead to high and low voltage variations. These large voltage fluctuations not only can burn out the generator but also potentially damage the vehicle's electrical components, with a relatively high probability. Additionally, it's quite likely to cause "abnormal" conditions in the battery. Other component-induced failures: Other electrical equipment might cause generator burnout due to short circuits, grounding, or wiring faults. Such malfunction phenomena can also affect the normal operation of the battery.

[MacJanelle]

With over a decade of experience in car repairs, I've seen countless cases of alternator failures. Wear and tear of core components is the most common issue. For instance, the carbon brushes inside the alternator, much like pencil lead, gradually wear down until they're too short, causing poor contact and triggering the battery warning light. Diode breakdowns in the rectifier bridge are also critical, especially prone to burning out in summer due to poor heat dissipation, which can halve the charging capacity immediately. Then there's bearing lubrication failure – particularly in older cars after driving through puddles, the bearings start making rattling noises. If not replaced, the entire rotor could be ruined. I recommend checking the alternator voltage every 60,000 kilometers. If it's above 15V, it means the voltage regulator is faulty, and prolonged overcharging can cause the battery to swell.

[SanJohn]

Once my car broke down on the highway in the middle of the night, and the tow truck driver said it was because the alternator burned out. He mentioned that alternators are actually afraid of three things: overheating, overloading, and moisture. For example, installing a high-power subwoofer that forces a stock 140A alternator to handle a 200A load can cause the coils to overheat and melt. When wading through water, the belt can fling water into the cooling vents, causing the rotor to rust and seize, rendering it useless. Even more extreme, some people use high-pressure water jets to clean the engine bay, leading to short circuits and sparks in the coils. He advised measuring the load with a clamp meter before modifying the electrical system and avoiding the cooling grille at the rear of the alternator when washing the car.

[Kimberly]

Last week, my neighbor's daughter had her car's alternator fail, and the battery light on the dashboard lit up like a Christmas tree. I accompanied her to the repair shop, where the mechanic explained the fault logic is straightforward: either it's not generating electricity (brushes worn out), generating unstable power (voltage regulator failure), or overcharging (rectifier breakdown). He particularly emphasized paying attention to squeaking noises, as they are early signs of insufficient bearing lubrication. If the dashboard brightness fluctuates with the throttle when the headlights are on, it's likely the voltage regulator is done for. Nowadays, alternators in new cars are connected to the ECU, and a failure might even trigger engine speed limitation.