How a car’s electrical system works?

Electrical systems in vehicles have become increasingly complex over the years, but they all include these basics: an ignition switch, a starter, an alternator, and a 12 V battery. In this blog post, we’ll discuss each component in an internal combustion engine (ICE) vehicle, explain how each connects to the other, and point you to resources for common issues.

Ignition switch

When you insert your key into the ignition or press the start button, you close an electrical circuit to the starter that ignites your engine, thus giving it the power to start.

To kick-start this process, the ignition system pulls energy from the battery by sending the spark needed to start the engine. However, it uses a high level of voltage to complete this job.

Whereas a vehicle’s battery runs on 12 V of power, the ignition switch will create somewhere between 20 kV and 40 kV, depending on the vehicle. This is why trying to turn on the ignition too often when your car won’t start isn’t a good idea: you’ll drain the battery faster.

Common issues

Look for these symptoms if you’re having difficulties starting your vehicle:

• Your engine has difficulties starting in the cold.
• The engine rotates but doesn’t continue running.
• The engine starts, but immediately stops.

Starter

If you’ve watched any movies or TV shows that took place about a century ago, you’ll see drivers using a hand crank to start the engine. Because this was inconvenient, arduous, and sometimes dangerous, the starter was invented.

The ignition turns on the starter—more accurately called the starting motor—to crank your engine so you can drive your car.

Common issues

The main problem with a starter is volt drop. This is when the starter doesn’t receive enough voltage to do its job. Extremely low temperatures can make this issue worse.

To diagnose any problems, an automotive technician will test the voltage. If the voltage is correct but the starter won’t turn on, the starter needs to be repaired or replaced. However, if the voltage is low, the technician will further inspect the circuit itself.

Alternator

The alternator is a primary component of the charging system. (In modern vehicles, it may be the only component.) It turns mechanical energy from the engine into electrical energy by transforming an alternating current (AC) into a direct current (DC).

Your vehicle needs a working alternator to charge the battery. If this component is damaged, at best, your vehicle won’t start. Worst-case scenario: your engine will stall, which can be dangerous at high speeds on the highway.

In addition, driving with a bad alternator can damage critical electrical components, such as power steering and the water and fuel pumps.

Common issues

Any of the following symptoms can signal a damaged alternator:

• dim or overly bright lights
• growling or squealing noise
• battery warning light on
• frequent stalling or trouble starting
• burning rubber smell

Some of these symptoms are similar to the symptoms of a dead battery. If your car shows any of these signs, though, take it in to your nearest NAPA AUTOPRO service centre so a professional can assess your vehicle’s electrical system.

Battery

Your starter pulls its initial energy from your vehicle’s 12 V lead-acid battery to ignite the engine. However, the battery also supports your vehicle’s other electrical needs, like your heating, ventilation, and air conditioning system (HVAC); stereo; device charging ports; and more.

These batteries comprise six cells of 2 V each. In each cell, you’ll find two plate groups. The positive plate groups are made of grids filled with lead peroxide in sponge form. By contrast, the negative plate groups are filled with porous lead. Separators keep the plates apart so they don’t touch and short circuit.

Next comes the electrolyte. This substance can be stored in different ways, depending on the construction of the battery.

• Flooded batteries: A liquid electrolyte fills the battery to just above the plates. This type is also called a wet cell battery.
• Absorbed glass mat batteries (AGM): The electrolyte is embedded in fibreglass mats. This produces a much more stable battery, so they are sometimes called maintenance-free batteries. You can learn more about AGM batteries here.

Common issues

A dead battery can ruin your day. You will need to jumpstart the battery again, which CAA Roadside Assistance and similar services can help you with. A three- to five-year-old battery that won’t jumpstart may need replacement or could signal another issue. More details on how to know if you need a battery replacement can be found here. You can learn more about battery problems here.

To reduce the chances of your battery dying, follow these tips:

• If you use your car mostly for quick errands, ensure you drive it for a half hour at least once a month.
• Turn off all electrical components in your car (e.g., lights, stereo, HVAC system, etc.) when you turn off the engine.
• Protect your car from extreme hot and cold temperatures.

Servicing your vehicle’s electrical system

While you can carry out some basic tasks on your own, such as installing a new battery, we advise seeking help from automotive technicians for any additional repairs to the electrical system.

You wouldn’t attempt to fix electrical problems in your home, so why attempt electrical repairs on your vehicle? High voltage can flow through the system, and some components are so intricately woven into one another that one error can cause extreme damage and even severe injury.

Visit your local NAPA AUTOPRO service centre for an assessment. Our automotive experts will be more than happy to help.