Electrical Wiring Problems? 9 Common Issues & Fixes

Electrical wiring in a car can be complex and hard to diagnose. Older cars have less wiring and circuits, while new cars have switches and circuits for almost everything you can think of.

Trying to diagnose an electrical problem can drive a person mad, so we’ve compiled a list of the most common issues and solutions to fix them.

This list should cover most of the problems you’ll face, and with basic skills and tools, you’ll be able to chase down any problem and find a solution.

If you can’t find the issues plaguing your car, be sure to seek help from an automotive electrician or a professional mechanic.

#1 – Your Battery Is Dead Or Dying

The battery in your car is one of the major components, and without it, you’ll be dead in the water (bad pun intended). We’ve written before on common problems with car batteries.

Diagnosing a dead battery is pretty easy. You jump in your car, turn the key, and nothing happens. No beeps, no lights, nada.

Leaving your radio on for too long without the car running or leaving an interior light or the headlights on are the usual suspects of draining a battery. Even a faulty starter or alternator can slowly drain a battery.

The harder problem is diagnosing a dying battery.

It may not hold a full charge, and that can allow it to drain quickly without the car engine running.

A dying battery can also cause issues with sensitive electronics that need a stable electrical system. You may continually see a check engine light or a diagnostic code resurface because of a dying battery.

If you think you have a battery issue, this article about common battery issues may help diagnose the problem.

How to Fix It

  • A fully charged battery should have a voltage greater or equal to 12.6 volts.
  • A dead or dying battery will have a voltage of 12.0 or less.

You can use a voltmeter to determine the voltage of the battery with and without the car engine running to know if the Alternator is working correctly.

Your battery should show a voltage between 13.6 and 14.6 volts when the vehicle is running, which indicates the Alternator is charging the battery.

If the battery won’t fully charge, it should be replaced. It could have a bad cell inside the battery, and you can’t repair it.

#2 – The Alternator Is Bad

As mentioned in issue #1, the alternator should produce a voltage between 13.7 and 14.7 volts when the engine is running. You can verify that with a voltmeter connected to the battery.

If the alternator doesn’t appear to be producing power, first check the wiring connections on the alternator, the wiring itself, and the battery cable connections to the battery.

A loose connection or a damaged wire can cause different electrical issues with your car.

If all the connections and wiring check out, it may be the alternator has gone bad. You can remove it and have it checked at a local auto parts store before buying a new one. If you take it to a mechanic, they can also have it checked.

A bad alternator can cause flickering lights and dim headlights, and your car will eventually run out of power as it drains the battery.

How to Fix It

If the alternator has gone bad, it can be replaced. Many can also be rebuilt with new internal parts while reusing the external housing.

You can check both options and decide which is the better choice.

#3 – Your Starter or Starter Solenoid Are Bad

Most of the time a starter or starter solenoid is bad, and they will still try to start your car on occasion.

Underlying electrical issues can fatigue a starter or its solenoid, and it will slowly start to fail without fully dying.

It may first start indicating a potential problem with a slow reaction to turning the key and starting the car. It may also take a few attempts at trying to start before it works correctly.

If you detect a problem or a change with the starter (or how you think the car should act), don’t put off diagnosing the problem. A bad starter can leave you stranded down the road.

How to Fix It

If the Starter or Solenoid are bad, they can be replaced.

Changing either component will just need basic hand tools like a socket and ratchet set. Be sure to disconnect the battery before changing parts to prevent an injury.

Read also, Car CPU Problems: 5 Most-Common Issues & Solutions

#4 – You Have A Short Circuit

Nothing will drive you crazy faster than a short circuit, especially if it comes and goes.

Short circuits are caused by a wire grounding out from a damaged wire coating or an electrical switch that has an internal issue. The issue may cause a fuse to blow, indicating which circuit it is connected to, or you can trace the location if it has a burning smell.

How to Fix It

A short circuit can be fixed quickly if you can find it.

A damaged coating on a wire can be insulated with electrical tape to prevent the short circuit from occurring.

Wiring harnesses that are too short can be stretched to fatigue or failure. Wiring that crosses sharp metal brackets or moving components can be worn and damaged, causing short circuits or, in the worst case, a fire.

#5 – You Have Bad Battery Cables

Bad battery cables can cause many wiring issues as they play a vital role in the complete electrical system. They can prevent the alternator from charging the battery. They can prevent your car from starting or intermittently allow the starter to work correctly.

Battery cables can become dirty, corroded, or loose and cause a number of issues with the electrical wiring, including slow charging, dim lights, or stalling.

How to Fix It

Before you assume the cables are bad, check that they are properly connected to the battery and on the vehicle.

If they are connected well, check that they aren’t corroded or dirty. Clean them if they are. If they are clean and well-connected, but still exhibit a problem, they should be replaced.

#6 – Your Fuses Are Blown

A blown fuse indicates a problem in the wiring circuit. A fuse is meant to protect the circuit from an amperage overload, which can indicate a short circuit or another similar problem.

If you’re a beginning to car mechanics, check out our article explaining everything you need to know about fuses.

Replacing a car fuse and relay

How to Fix It

Replacing a fuse is an easy process once you identify where it is. Many newer cars have multiple places for fuses to hide, including the dashboard or in the engine bay.

Your owner’s manual will indicate where they are and you can remove and replace the culprit.

If you replace a fuse and it blows quickly, there is another issue to diagnose. Find what is causing the fuse to blow before replacing it.

#7 – Your Lights Are Behaving Erratically

Your headlights draw a significant amount of power from the electrical system, and they are a great indicator of electrical wiring issues.

Car lighting uses a system of fuses, wiring, relays, and switches. A loose connection, a blown bulb, or a damaged wire can cause small or large electrical issues.

How to Fix It

Lighting either works or it doesn’t, even if it’s dim.

A bad bulb can be replaced, but if it doesn’t work there may be another issue preventing it from lighting correctly.

There may be a blown fuse, a bad switch, or a damaged wire preventing power from going to the bulb.

#8 – Your Fuse Box Has Gone Bad

You wouldn’t think a complete fuse box could go bad, but it can happen.

Fuse boxes are designed to prevent short circuits, but under the worst circumstances, the circuits can overload and damage the fuse box itself. That may allow short circuits to occur everywhere in the car and cause multiple issues.

How to Fix It

The fuse box can be replaced, but it’s a big job to do. Only attempt it if you’re confident in your skills. Otherwise, let a professional tackle the replacement.

#9 – Your Spark Plugs Have Failed Or Are Failing

Spark plugs ignite the fuel in the engine combustion chamber. They typically are connected to a spark plug wire or a coil that transfers the power to them to ignite the fuel mixture.

They can fail over time or start to fail because of age or other electrical issues. This can cause your car to run poorly or stall.

How to Fix It

Spark plugs are replaceable and can be done with basic hand tools like a socket and ratchet.

There are specific spark plug sockets that have rubber insulators inside to prevent damage to the spark plugs.

Change the plugs when the engine is cold to prevent damaging the threads on the cylinder head or burning your hands on hot parts.

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