Unlike a loud engine knock or noisy exhaust, car electrical problems can be harder to diagnose and pinpoint. Many functions that operate in your vehicle require a sound electrical connection that relies on a series of wires, a battery, the alternator, and the vehicle's computer.

Modern vehicles, in particular, have extremely complex electrical systems, as almost everything the driver interacts with are connected in one way or another to the electrical system.

This article will summarize common vehicle electrical problems and how to troubleshoot them so you can decide how to proceed when it comes time to fix the problem.

Car Problems that may be caused by Electrical Problems

Vehicle Will Not Start 

This is one of the most common electrical problems people encounter with their cars.

When you put the key in the ignition, if it is not starting as it should then you probably have a problem with one of three electrical components - the battery, the alternator, or the starter.

Batteries usually do not fail right away - they usually give a warning sign that they need to be replaced before they die completely.

One warning sign might be a slower turning starter (for instance, the car starts but it takes longer than usual for it to turn over). It is also important to keep the battery terminals clean and free of oxidization.

A functioning battery can act as a dead battery if the terminals are corroded. Battery terminal cleaner can be purchased at any auto parts store.

The problem is likely with your battery if the interior lights are on when you open the door but the car will not start. In such cases, you may hear several clicks when you try to start the car.

Conversely, if the interior lights are off and the car won't start, you probably have a dead battery.

Dashboard Lights Flicker or Dim

If your dashboard lights are flickering or your headlights dim while you're driving, this is also a sign of an electrical problem.

Depending on the cause, the problem could be with your battery, alternator, or voltage regulator.

The voltage regulator is responsible for regulating how much electrical output the alternator makes.

So if it fails, it can cause issues with charging and electrical components because the alternator is either putting out too little voltage or too much voltage.

If the problem is with the battery, it may be charging slower or having difficulty holding a charge, which can result in the dashboard lights dimming or flickering.

Lights or Brake Lights Not Working

A third common electrical problem with vehicles is if the headlights or brake lights are not working but the rest of the car is running fine.

This could indicate a problem with one or more of the fuses. The purpose of a fuse is to protect the wiring in a car and not the electrical device that the fuse is connected to. So if a fuse is blown, it's more likely that something else is causing the issue.

For instance, if you replace the fuse and then it blows again, it's most likely shorting out somewhere in the wiring.

How to Fix Car Electrical Problems

In modern vehicles, fixing electrical problems is not always easy but it can be done with a few basic tools and a little bit of basic knowledge. The first tool you'll need is a multimeter, which measures voltage and resistance.

Alternatively, you can use an ohmmeter to measure resistance and a voltmeter to measure voltage. A multimeter performs both functions.

Keep In Mind
Before disconnecting wires, eep track of colors of wires and where they connect - it is helpful to take pictures before you start so that you know where wires belong when it comes time to reconnect them.

For every device in your vehicle that requires electrical power, there is a minimum voltage that is necessary for it to operate correctly.

To check if a certain device is working as it should, you can check the voltage by measuring it at various load points on the car. 

Check the Battery
The first step in discovering an electrical problem is to measure the voltage output of the battery using your multimeter or voltmeter.

Disconnect the battery from the car and make sure all lights are off. If the key is in the ignition, make sure it's turned to the off position.

Connect the red lead to the positive battery terminal - it is red and usually marked with a + symbol. Connect the black lead to the negative battery terminal - it is black and usually marked with a - symbol. If the voltage reading is around 12.66V, it means your battery is fully charged.

If the voltage reading is more than 12.43V but less than 12.66V, it means your battery is about 75%-90% charged and is still operable. If the voltage reads less than 12.4V, it means the voltage output is too low and the battery needs to be charged. One option is to jump-start it with another vehicle using jumper cables.

If you choose this option, it's best to go for a 20-30 minute drive (instead of a series of short trips) after getting it started to ensure the battery gets fully charged. If the battery is four years old or more, it may be time to get it replaced.

Some batteries last longer than others, but as a general rule, most car batteries last about four years.

Check the Alternator
If the battery voltage levels seem normal, the problem could be with the alternator. Testing the alternator assumes you can start the car. If the battery levels are normal, you should be able to. Start the engine.

Next, using the leads on your voltmeter (or multimeter), connect the red lead to the red terminal connector on the alternator. Connect the black lead on some metal part of the car for a ground connection.

Make sure your voltmeter is set to the 20V setting. If the alternator is operating properly, the voltage should be around 14 volts.

Sometimes the reading will be a little bit under that value and sometimes it will be a bit over that value. Values between 13.8 and 14.2 are good.

If the voltage reading is excessively high, it could be that the voltage regulator is going bad. If the reading is lower than normal, the problem could be a number of different things.

Try revving the engine to about 2000 RPMs and see if the reading changes. If the voltage is normal when revving it, your alternator is good.

If the voltage is still too low even with revving it, the alternator probably needs replacing.

Checking Load Points Voltage and Ground Connection
To check whether or not a particular device is working properly, check its load points using the leads on your multimeter.

You can also check your ground connection this same way. If the voltage is zero at these points, it's possible the fuse that protects that device needs to be replaced.

Remember not to replace an existing fuse with one that has a higher current rating as the wires are not designed to carry that much current. If a fuse does continue to blow, then the most likely causes are:
    a failed electrical component (like a motor or electronic device)
    a wire that has had its insulation compromised and is grounding out

Corroded Wires or Damaged Wiring Harness
Be sure to check for wires that are corroded as well. To discover whether or not a series of wires are damaged, check for voltage differences along with it.

If there is a voltage drop of more than 0.1V along with two points of the wire, it needs to be replaced.

Another common electrical problem is damaged wiring harnesses. Wiring harnesses are collections of wires that supply power to the engine, transmission, or other vehicle components.

Some of them are encased in insulation and sometimes this covering can deteriorate, leaving the wires underneath exposed, which can cause devices to short out. In this case, replacing the wiring harness should solve the problem.