What Causes Unstable Voltage in a Car Alternator?
2 Answers
Voltage instability can be attributed to the following two aspects: 1. Voltage deviation: Over a certain period, the actual voltage amplitude changes "slowly" and deviates from the rated voltage. The deviation is steady-state, meaning the voltage is either too high or too low. Voltage deviation is mainly influenced by the location and operating time of electrical equipment, such as lower voltage at the end of a line or higher voltage during late-night hours. To address this, it is essential to correctly select the transformer's voltage ratio and tap settings, reasonably reduce line impedance, improve power factor, implement appropriate reactive power compensation, and automatically adjust the capacity of reactive power compensation equipment based on voltage and load changes. Additionally, adjusting the operation mode according to the power flow distribution of the power system and employing load regulation methods, such as using on-load tap-changing transformers, can help mitigate voltage deviation. 2. Voltage fluctuation: Voltage fluctuation generally occurs due to changes in the power grid's operation mode, seasonal variations in power load, or faults and malfunctions in certain power grid equipment.
When I notice the dashboard lights flickering or the battery warning light comes on while driving, I know there's an issue with the alternator voltage. There are usually several causes: the alternator belt may be aged or loose, causing slippage and unstable transmission; the voltage regulator might be faulty, unable to control output fluctuations; or internal diode damage could lead to discontinuous current flow. These issues can make the car lights dim and brighten unpredictably, result in insufficient battery charging, affect electronic accessories like the audio system and air conditioning, and even cause premature battery failure. When this happens, I first check the belt tension and for cracks, making simple adjustments if possible. If that doesn't work, I measure the battery voltage—it should stay between 13-14V after the engine starts. Such instability poses significant risks, especially at high speeds, so I recommend not delaying and promptly visiting a repair shop. Often, replacing the faulty parts solves the problem.
