Automotive Alternator Problems and Solutions

The primary purpose of an automotive alternator is to charge the battery after it has supplied the high current needed to start the engine. Although many things will reduce the amount of available power in a car’s battery, starting the engine provides the biggest hit.

This is due to the battery supplying 100% of the needed power for starting. Once the engine is running the charging system is responsible for producing enough energy to meet the demands of all the loads in the electrical system plus a little extra to provide a continuous surplus. Accessories like headlights, turn signals and Interior blower motors get their power after start up and are therefore powered by the charging system.

Alternator Operation

An automobile charging system generates its alternating current by taking the mechanical energy provided by the engine crankshaft via the drive belt that rotates the alternators pulley. Like many automotive systems the alternator works on the principles of magnetism to change this mechanical energy into electromotive force.

To be more specific the pulley is spinning a pair of magnets with different polls inside of a stationary coil of conductor wire called the stator. As the spinning north and south poles of the magnet passes the conductors they induce voltage that first flows in one direction and then in the other which gives the voltage produced the title of AC (alternating current). The problem is automotive systems run on direct current so this AC voltage is converted to DC through a series of diodes known as a rectifier bridge.

Voltage Control and Regulation

The alternator is capable of putting out extremely high voltages. Since the automotive system is designed around 12 Volts the output needs to be controlled and managed to protect the battery and electronics. The component responsible for this is called a voltage regulator. In simple terms this device can increase the rate of charge when the battery is low and demand is high and reduce it to a trickle charge when demand is less.

One of the most important tasks of the component is to prevent catastrophically high outputs that could damage expensive electronic components. The fail safe that are designed into the charging system are often integrated into the regulator. These devices use to be separate and serviceable in older vehicles. Ford used external voltage regulators well into the 80s. Now vehicles have moved the regulator inside the alternator. Therefore voltage regulator failures often require replacement of the alternator.

Signs of Alternator Problems

Most vehicles are equipped with two devices to help monitor the operation of the alternator. The first is the charge warning light. This light is a simple on off indicator that comes on when voltage output is below the minimum specifications. At one time the alternator gauge was considered an option but now more common as standard equipment .These can be digital or analog but basically show how much voltage is being produced while the engine is running.

Drivers can keep an eye on this information and get an idea of how things are working in the charging system. Most alternators will have a maximum output of around 15 V. When the engine is first started or the vehicle has been sitting for a long time it would be common to see alternator output close to this maximum range. As the vehicle is run for a while this should reduce as the charge level returns to the normal range.

Vehicles that have a red warning light on or show unusually low or high levels of charge on the alternator gauge should be connected to a charging system tester. These testers check the output of the alternator to verify problems but can also test battery condition. Battery problems can make it appear the charging system is not functioning as per design intent and put extra stress on the alternator as it tries to charge the worn out battery.

Alternator Service

Alternators include wearable parts like brushes, and bearings. Although car makers state that these are designed to last the life of the vehicle that statement is debatable. If you keep the vehicle long enough you are likely to run into a situation where this will need to be serviced. Noise generated from failing bearings can be unsettling and send drivers in for diagnosis. Low output or a warning light is another reason to seek service.

On automobiles from the mid-1990s and older, many of these wearable parts were available in rebuild kits or purchased separately. The alternator could be disassembled and brushes and bearings replaced. Individual parts such as rectifier bridges and diodes were also available and replaceable. In the mid-1990s vehicle manufacturers started discouraging the repair of factory installed alternators. They stopped making the parts available and stamped non-serviceable on the casting.

Now drivers are forced to buy new or reconditioned alternators at premium prices. Fading are the days of replacing just the items that have gone bad like a voltage regulator or diode trio. Soon all consumers will have to replace the assembly. There are a few companies left, like alternator parts where you can purchase upgraded alternators that provide additional output when required by adding additional accessories to an automobile. This company also specializes in fixing known problems and common failures with factory parts.

Having a healthy alternator is important to anyone who drives a car. Its main function is to recharge the battery after starting the engine. It also supplies the power needed to run accessories after the engine is ignited. Indication of problems can come from dash mounted warning lights and alternator gauges showing low output. Failing bearings can generate levels of noise that forces drivers in for diagnosis and repair. On older vehicles rebuild kits are still in circulation but newer vehicles will probably have to settle for rebuilt or brand-new replacement parts.