The 9 Most Common Car Electrical Problems

The average car contains nearly one mile of copper wire. Most newer vehicles are heavily computerized and have around 30 modules. Is it any wonder car electrical problems are so common?

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The most basic gas-powered car today is incredibly dependent on its electrical system, and that’s only going to continue as cars become more tech-heavy. Electrical issues with car systems can be tough to diagnose and repair, but many are relatively common. You just need to know what you’re looking for.

These are nine of the top car electrical problems you might encounter and the ways they might show up.

Common car electrical problems

Some car electrical problems are simple DIY repairs. Others require a trip to the mechanic. Even if it’s not a repair you can do on a Saturday afternoon, you can better inform the technician about what’s going on and what you’ve done so far, hopefully resulting in a lower repair cost.

Bad alternator

The alternator converts the engine’s mechanical rotation into electrical energy. The electricity generated by the alternator primarily powers the car’s functions. The alternator also recharges the battery so there’s enough juice to start the car.

When the alternator quits, the car’s electrical functions rely on the power in the battery. Eventually the battery will drain, stopping the car’s electrical operations. The engine will stall once there isn’t enough power for the fuel pump, ignition and injectors.

If your alternator has given up the ghost, there are really only two options: Install a new one or take it into an auto electrical repair shop where it can be rebuilt.

Faulty starter motor

The engine’s starter motor is a high-torque electric motor that cranks the engine to start. A small gear on the starter engages with the flywheel or flexplate to force the crankshaft to move, kickstarting the process. The starter motor disengages when the engine is running.

A starter can fail in a few ways. Mechanically, the starter’s shaft might not extend far enough to spin the flywheel. Electrically, the starter solenoid can become corroded or burnt out, preventing the starter motor from spinning when you turn the key.

Although you can’t fix a starter while it’s in the car, you might be able to get it to spin in a pinch by tapping on it with a hammer. Otherwise, you’ll need to tow the car to a repair shop that specializes in diagnosing auto electrical problems.

Broken wire

Wiring goes to all corners of your car. Harnesses enter each door. Wires snake all over the engine, where they vibrate, heat up and get exposed to fluids. Broken wires are relatively common and can affect virtually any of a vehicle’s systems.

Wire insulation can crack, get pinched or pull apart. They can develop corrosion. A broken wire stops the flow of electricity dead in its tracks, so whatever it’s attached to will stop working.

With a mile of wiring in your car, tracing the barely visible break is almost impossible without diagnostic equipment. Have a mechanic trained in automotive electrical troubleshooting deal with the issue.

Blown fuse

Fuses protect electrical systems from damage. An electrical surge of unregulated power can cause electric motors, sensors and modules to burn out. If there’s a fault in a fused circuit, the fuse protects the rest of the electrical system by breaking the circuit. The fuse is designed to blow if the electrical draw is too high for the circuit.

Fuses can also corrode, and occasionally you can have a fuse with high resistance even though it doesn’t appear blown.

A blown fuse is a simple repair. Pull the old fuse out and install one of the same amperage. If the fuse blows again, there’s likely a problem on that circuit in need of troubleshooting.

Misfiring spark plugs

Spark plugs fire in succession to ignite the air-fuel mixture at the right time. They have a ceramic insulator to prevent loss of power outside of the combustion chamber.

Spark plugs need an exact gap between the ground electrode and center electrode, and they need to stay relatively clean. The insulator must also remain intact. A cracked insulator will leech power and prevent a strong spark, and an oil- or fuel-fouled spark plug will cause a misfire. The same is true if the electrodes are worn or the gap is too large or small.

Spark plug replacement is a routine maintenance item—a job easily undertaken by a DIYer in most cases. Simply swapping out the spark plugs will restore your car’s operation as long as that’s the only fault.

Dead battery

The battery’s main purpose is starting the engine when the key turns the ignition, placing a huge strain on the battery in the process. It’s also a backup power source if the alternator quits.

If the battery is completely discharged or won’t recharge, your engine won’t start. Lights will be dim at best, and electrical functions inside the car won’t work.

Sometimes, all a dead battery needs is a recharge. An auto parts store can bench test the battery to see if it’s still in good shape. If that doesn’t work, changing the battery is the solution, and that usually isn’t complicated.

Poor ground

Think of an electrical system as a complete loop. Completing that loop is the ground wire. Every circuit has a ground of some kind, either with a dedicated wire, a ground strap or a physical connection with a grounded component such as the engine block. That all connects to the battery’s ground terminal to complete the circuit.

A loose, corroded or broken ground can cause several issues. Any of those problems can affect a single or multiple systems at once, ranging from no power in the car to an intermittent dim bulb and everything in between. They often remain a mystery for a long time.

Finding a bad ground can take hours. The bad ground might not be visible, and intermittent systems make it difficult to know if you’ve found or corrected it. This is a job for someone familiar with troubleshooting auto electrical problems.

Faulty sensors and solenoids

On average, cars have between 60-100 sensors that perform roles such as monitoring engine vibration and measuring exhaust oxygen content. Solenoids are similar, except they perform functions such as opening and closing valves.

If a sensor or solenoid fails, the system won’t operate as designed. The inconvenience could be small—for example, a dome light that won’t shut off. More serious issues, such as the engine overheating or the transmission malfunctioning, are also possible.

If you know which part needs to be replaced, the process can be as easy as removing the part and installing a new one. In most cases, determining whether the problem is with the part or something else on the circuit will need to be diagnosed first.

Faulty module

Small computer modules with dedicated functions control almost every system in a modern car. Modules power circuits and regulate solenoids, directing power where it’s demanded. Modules are used for everything from the anti-lock braking system and fuel pump to electric steering and powertrain.

When a module quits or has a fault, there’s usually a communication issue. Symptoms can be wide-ranging, primarily because challenges come with determining if the whole module is bad or just an individual circuit is.

A faulty computer module needs to be replaced. Many of the new modules need to be programmed with the vehicle information. You can install the module quickly on your own, but a technician will need to program it once installed.

Signs of car electrical problems

Some concerns point to a mechanical issue such as whirring or clunking. Others will send you down the path of an electrical diagnosis. Here are some signs you may be facing an electrical issue rather than a mechanical problem.

Lurching or rough idling

If your engine isn’t running smoothly, there may be a misfire. If your engine is sputtering and feels like it’s going to stall while you idle, or if your car feels underpowered then surges sometimes, this is potentially the issue. One or more spark plugs may be fouled or damaged.

Check engine light

“Check engine light” is a misleading term. In most instances, there isn’t a problem with the engine but rather a sensor or fault in the emissions system. One of the most common causes for a check engine light is a faulty oxygen sensor.

Dim or inoperative lights

An electrical short or a bad ground is a relatively common problem in lighting circuits. If you have a bulb that needs to be replaced often or your headlights or brake lights are dimmer than normal, there’s an electrical issue to address.

Blown fuses

If you find a blown fuse, the first step is to change it. If it blows again, there’s an excellent chance a circuit is grounding or a wire is rubbing—or there’s excessive draw somewhere on the circuit.

Hot or plasticky burning smells

Several issues can cause burning smells—for example, a plastic bag stuck to your tailpipe. An overheating electrical wire or component can have a similar hot or plastic burning smell. If a circuit has too much resistance, it heats up the weakest part on the circuit—typically a wire. This might produce a red-hot glow and cause an odor as the wire insulation burns.

Car won’t start

A battery typically lasts no more than five years, and that’s one of the most likely reasons your car may not start. If the battery is at fault, your engine won’t turn over or will crank very slowly.

Even if the battery is fine, a burnt-out starter, broken wiring or one of many bad sensors can also prevent a car from starting.