Rotating electrics 26 Finding the fault behind starter and alternator failures Autoelectro’s Harnek Bhogal explains what the company learns from returned starter motors and alternators, the tell-tale signs technicians should look for and why finding the root cause matters before fitting a replacement. Understanding why a starter motor or alternator has failed can help technicians identify an underlying vehicle fault before fitting a replacement and reduce the risk of the same problem happening again. For Autoelectro, returned old cores provide an opportunity to investigate those causes. The Bradford-based remanufacturer tests, inspects and strips returned units, using the volume of components it receives to identify common failures and trends. “By analysing the volumes of returned old cores we look to identify common failures and trends to work backwards to determine the root cause which helps ensure the underlying fault can be addressed before a replacement part is fitted, therefore reducing the risk of the same problem happening again,” explained Autoelectro’s Harnek Bhogal. Look beyond the alternator One of the most common alternator failures Autoelectro sees involves clutch or freewheeling pulleys that have seized or failed altogether. However, the company says this is more often than not caused by excessive lateral load. This can result from a tensioning or drive belt-related issue where pressure on the alternator pulley system becomes too great and, over time, causes the pulley mechanism to fail. Autoelectro says this can be misdiagnosed as a faulty alternator pulley or bearing. Harnek explained that when the company sees a pallet of old cores with the same failure, it is highly unlikely that they all had faulty pulleys; rather, they were fitted to the same vehicle engine with the same inherent tensioning issue. The removed component can also provide clues. Fine black dust on the front of an alternator casing indicates the belt has been slipping on the pulley grooves as a result of a tensioning issue. If the alternator is physically wet when removed, Autoelectro says this indicates a leak somewhere in the engine, usually involving coolant, fuel, water or oil. What burnt-out starters can reveal With starter motors, Autoelectro says the main issue it sees with returned old cores is units that have burnt out. This occurs when they become stuck in the engaged position, causing the starter’s internal components to become too hot and fail. The customer may report that the starter does not engage or simply clicks. Autoelectro says the underlying cause is more often than not a faulty ignition switch that leaves the starter wiring engaged, poor battery condition resulting in the starter having to work overly hard to crank the engine, or another issue such as a bad earth.
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