Car Fule

How to diagnose an alternator failure?

It is important to be aware of the signs indicating an alternator failure.

The battery indicator lights up

The battery warning light on the instrument panel lights up continuously means that the accumulator is responsible for supplies the motor and accessories with electricity. Indeed, it is designed to take over when the alternator is out of order. Therefore, it is recommended to have it repaired or replaced as soon as possible. If the battery is always used, even when the engine is running, it may no longer be able to supply the energy required for the next start.

Abnormal noises under the hood

When the engine is running and a squealing or squealing is heard, the first reflex to have is to check the tension of the accessory belt. Indeed, these abnormal noises can come from an overly slack belt. As a result, the alternator may not be able to charge the battery properly, as the coil spins at an irregular rate. In the long run, the strap ends up tearingor even break.

Perform the test using a multimeter

This device is appreciated for its versatility and the high accuracy of the data it displays. In voltmeter mode, it allows you to measure the alternator voltage. Once the engine has started, the first step is to press the accelerator pedal until reaching 2000 rpm. Then all you have to do is refer to the indications displayed on the multimeter screen:

• A voltage between 13.3 and 14.7 volts indicates that the alternator is functioning correctly;
• A voltage lower than 13.3 volts is a sign that the alternator is out of order and that it must be replaced as soon as possible;
• If the measured voltage is greater than 14.7 volts, it means that the regulator is no longer able to limit the supply of electricity. Consequently, the accessories may burn out due to the generated overvoltage.

Good to know

A worn alternator does not prevent the car from starting. However, it risks stalling at any time.

The above indications are not not valid for recent cars fitted with the “Start and Stop” system. Indeed, their alternator is able to perform its role, even if the measured voltage is 12 volts or 16 volts.

Why call a mechanic?

It is recommended entrust the checking of the condition of the alternator to a professional. Indeed, only the latter is able to check the condition of all the elements essential to the proper functioning of the vehicle. The budget to be expected depends on the type of failure, the duration of the intervention or the parts to be replaced. To settle the invoice, it is preferable to opt for payment by check, which is more secure, or by bank transfer, which is faster.

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