How to Test Your Alternator and Charging System

Your Mazda relies on an uninterrupted supply of electricity to power all its electrical features. Your alternator ensures this happens, so when your alternator goes on the blink, everything that relies on electrical power is affected. Read on as our article takes a detailed look at all you need to know about alternators and how to test your alternator and charging system.

What is an Alternator?

The alternator recharges the 12-volt battery fitted in your Mazda. Think of your car's alternator as a mini electrical generator spun via a rubber drive belt and pulley system connected to the front of the engine's rotating crankshaft. The fast-spinning alternator initially creates electrical energy in the form of alternating current (AC), which is then converted to direct current (DC) courtesy of the rectifier found in the alternator. The electrical current created is used to recharge your Mazda's battery and power all the onboard electrical systems while the engine is running.

What Does Your Charging System Do?

The charging system generally refers to the alternator, the fuses, the battery, and the wiring harness that all function to keep your car's electrical systems alive. The primary function of the charging system is to recharge the battery fitted in your Mazda to its ideal level of around 12.6 volts at rest or 13.5 to 14.7 volts when the vehicle's engine is running. This recharging function ensures there is always sufficient power available from the battery when you switch on the aircon fans, for example, or power your side windows down.

Symptoms of a Weak Alternator

When learning how to test an alternator, it's key to know what symptoms to look out for.

All cars fitted with an alternator will feature a charging light. This light is mostly located on the dashboard among the instrument gauge cluster and is typically a red light with a battery icon. When this illuminates fully or flickers on and off, you know you have a problem.

Some symptoms of a weak alternator are easy to spot, aside from the flickering or dull ignition light. Your vehicle's electrical systems will not function correctly. Dull headlamps or even a feeble sounding horn will highlight a weak alternator. Eventually, your Mazda's battery, even if new, will not recharge sufficiently, and a slow cranking engine when trying to start can be attributed to a weak alternator.

How to Test the Alternator

Learning how to test an alternator is necessary to establish whether the alternator is indeed faulty. Once you have identified an issue, there are some quick and easy tests that can be performed, but you will require the right tools.

Visual Inspection of the Alternator

A visual inspection of the alternator is your first stop. Let's dive deeper into some things to inspect.

Inspecting Wires and Connections

A visual inspection of all wires and connectors along the charging system's wiring harness can reveal the problem. Many times, a simple issue like a loose battery terminal turns out to be the problem.

Checking the Drive Belt

A failed or missing drive belt is easy to spot. A thrown drive belt that has completely left the pulleys is an easy diagnosis of an undercharging alternator. A loose V-belt will also slip on the pulleys, causing the alternator to charge weakly.

Testing the Alternator with a Multimeter

If you have one available, a voltmeter is a great way to test an alternator. This device should be used to accurately check the battery voltage output while the engine is off and running.

Checking Battery Voltage Before Starting

The voltmeter's leads should be connected to the battery terminals before starting the car's engine to obtain a reading. A healthy reading is around 12.6 volts. Anything below this level indicates a low battery charge.

Testing Voltage with the Engine Running

Ensure the engine is running and the car is idling before connecting the multimeter's leads first to the positive terminal and then to the negative terminal. With the engine idling and the voltage function set on the multimeter, the reading should be around 13.5 to 14.5 volts. A significantly lower or higher reading could indicate an alternator problem.

Interpreting the Results

As we've already learned, the voltage level reading should point us in the right direction. A reading on the battery of 13.5 to 14.5 volts while the engine is running is good; anything below that reading should prompt seeking professional help.

What If Your Alternator Isn't the Issue?

A low reading of below 12.6 volts on the car's battery means that the battery may possibly be the culprit. A faulty battery or an old battery will not hold a sufficient charge even if the alternator is working at 100 percent.

Inspecting Fuses and Fusible Links

A thorough investigation of the charging system includes all fuses, and these, along with the fuse holders, should be checked for continuity using a multimeter to establish that there are no breaks in the wiring system.

Voltage Regulator and Sensors

Unless you are qualified in auto electrical diagnosis and possess the right equipment, it's best to have the alternator, along with the voltage regulator and sensors, tested professionally. Correct testing makes use of diagnostics equipment to help establish any faults.

Next Steps if Issues Are Found

When testing your alternator, if you have made the correct diagnosis and the alternator or any of its components, such as the regulator, are found to be faulty, the alternator should be removed for repair or replacement.

When to Seek Professional Help

Not all of us are DIY mechanics who can quickly sort out fixes like a loose belt or wire, and if the task of removing the alternator for repair seems beyond your skill set, then it is best to seek professional help.

Replacing the Alternator

It is best to compare the costs of repair vs. replacement of an alternator. Typically, a replacement part works out better value in the long run, especially for older vehicles.

Get Alternator and Charging System Service at Central Mazda

Choose to have your alternator and charging system service done at Central Mazda in Plainfield, CT. Not only does Central Mazda offer a Genuine Mazda Service Center with trained Mazda technicians, but our professional team wants your Mazda to receive the very best care when it comes to service and repairs.