Troubleshooting Aircraft Alternators: A Guide to Identifying and Resolving Issues

As a vital element to aircraft operations, the electrical system ensures the proper functioning of numerous onboard systems and assemblies. Among these, the aircraft alternator in particular plays a crucial role in not only generating electrical power, but also charging the battery. However, like any other mechanical device, these complex apparatuses are prone to occasional issues. In this blog, we will explore the common problems of aircraft alternators, as well as provide troubleshooting tips to help identify and effectively resolve these impediments.

Inspect the Alternator Belt

One of the primary causes of alternator failure is a loose or damaged alternator belt. For this reason, we recommend starting the troubleshooting process by inspecting the belt for signs of wear, cracks, or excessive slack. A properly tensioned belt should have just enough give to deflect approximately half an inch. If the belt is not properly aligned with the pulley system, you will need to adjust or replace it as necessary.

Check the Voltage Regulator

The voltage regulator serves in preserving a steady electrical output from the alternator. However, if the alternator is not delivering a consistent voltage, it may indicate a faulty voltage regulator. When this occurs, use a multimeter to measure the output voltage while the engine is running at various RPMs. If the voltage fluctuates significantly or falls outside the acceptable range specified by the aircraft manufacturer, it may be necessary to consider a replacement.

Examine the Alternator Brush

The alternator brush is responsible for maintaining electrical contact with the rotor, permitting the generation of electricity. Over time, the brush may wear out, which will lead to a loss of contact and subsequent alternator failure. To mediate this, inspect the brush for signs of excessive wear or damage, and if the brush appears worn or the length is below the manufacturer's recommended specifications, it should be promptly replaced.

Check for Loose Connections

Alongside other potential issues, loose or corroded electrical connections can hinder the flow of electricity, leading to alternator problems. In this case, thoroughly inspect all electrical connections, including the alternator terminals, battery cables, and ground connections, ensuring they are tight, secure, and corrosion-free. If you discover any corroded terminals, clean them, then apply dielectric grease to prevent future corrosion.

Test the Battery

A weak or faulty battery can place additional strain on the alternator and potentially cause premature failure. Using a load tester, test the battery to determine its health and capacity. If the battery is weak or failing, replace it to guarantee proper system performance.

Monitor Voltage and Amperage Output

To diagnose alternator issues accurately, monitor the alternator's voltage and amperage output using suitable testing equipment. After that, compare the readings with the manufacturer's specifications. If the output is consistently below the recommended values, this reading may indicate a problem with the alternator's internal components and needs further evaluation.


Maintaining a reliable aviation electrical system is crucial for the safety and functionality of an aircraft. More than that, troubleshooting aircraft alternator issues requires a systematic approach to identify and resolve potential problems. Keep in mind that if you encounter any issues beyond your expertise or require specialized assistance, consult with a qualified aircraft maintenance professional.

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