Symptoms Of Bad Battery Cables: Causes and How to Fix?

Are you having problems starting your car? Your first reaction will probably be that you have a serious malfunction like a bad alternator or battery. However, I would like to point out that your vehicle is a collection of several components and individual parts. The car powering problem can be a result of a bad battery cable. Knowing the Symptoms of bad battery cables helps you detect the problem early and fix it.

While battery cables have a simple mode of operation, when there is a failure, the cables can cause problems to the electrical system. The electrical system powers everything including starting your car, car lights, AC system, monitoring systems, and onboard computers. Without electricity flowing into the electrical system, you can’t start your car.

What Is a Battery Cable?

Battery cables connect the battery directly to the vehicle’s electrical system. Mostly, the cables have heavy-duty insulation covering because of the high power and current flowing through the heavy gauge wires. The immense pressure placed on the cables is why when you have a bad battery cable it affects all the electrical systems of the car.

When the vehicle won’t start, there is a problem with your battery cable. For example, there may be corrosion inside the battery cable. Corrosion provides high resistance to your electrical circuit, preventing sufficient current flow to power the car or fire up your electrical systems.

The viable option left is to test the battery cables and determine whether they are in good condition or bad. Before diving deep into how to test battery cables, let’s examine the symptoms of bad battery cables.

Symptoms of Bad Battery Cables

A working car battery cable should allow current flow and power to your engine. This only happens if the cable is in good condition. So, what if the battery cable fails? How do you know if you have bad battery cables? There are obvious signs of trouble that alert you of a problem with your battery cables. The signs help you take action to remedy the situation before you experience a complete electrical system failure.

So, what are the signs of a bad battery cable?

how to test if battery cables are bad

Your car won’t start

The car starter is a major component of the vehicle’s electrical system. If there is no spark or juice, your car doesn’t start, which is bad news. The first sign of a problem is when the car is cranking or your engine is turning over when you try to start it and takes longer than usual.

These are indications of less juice or electricity flowing from your battery to the spark plugs. Low power means a slow crank, and the engine experiences difficulty when starting. You have to wiggle the battery cable to start the car.

The cables transfer power from your car battery to the vehicle’s electrical system. A problem with the cables affects the current flow and it can’t conduct power. To start a car engine, you need considerable cranking power.

You can experience slow cranking or you hear clinking sounds when you start the car, which means there is less current passing through the cables to start the engine.

Corroded battery terminals

There may be corrosion inside the battery cable. How do you know? Stick your head under the hood and examine the battery terminals. If you notice signs of corrosion, then it explains why the car is having a problem starting.

Specifically check the battery terminals where it’s hooked up with the battery cables. Corrosion is a sign of damaged battery cables. Mostly, it’s caused by the battery acid heating because of the hot engine temperature as you drive. The hot acid damages the cables, causing corrosion in the terminals.

Over time the vapor from the hot engine operation corrodes the battery terminal, causing a buildup resulting in increased resistance which can block current flow. Corrosion can seep into the cable, corroding it on the inside. The best remedy is to replace the battery cables.

Dim headlights

This is one of the bad negative battery cable symptoms. You experience flickering fog lights and dim headlights. The dimness means there is insufficient electricity flowing to the headlights because you have a poor connection to the car battery.

The poor connection to your battery terminals could be because of corrosion making your car lights dimmer or flicker when driving.

Low voltage battery

When the positive battery cable is damaged, your alternator won’t achieve full charge giving your a low voltage battery. A normal car battery voltage reading is 12.6V when the vehicle is off and between 13.7V to 14.7V when your vehicle is running. If you get a different voltage reading, then the positive battery cable has a problem or you have a bad alternator or battery.

Full system shutdowns

This is by far the most serious as your electrical system fails completely. The vehicle receives no electrical power, and it affects all elements of the vehicle relying on electricity to function.

Nothing happens when you insert the car key and turn it on, meaning the electrical system is dead. Also, if you turn on your radio or headlamps, you get nothing. The expert recommendation is to replace your battery cables when the first symptoms show to avoid getting to this stage of complete electrical system failure.

This happens because the cables are corroded to a point where there is no clear connection with your battery, hence the vehicle’s electrical system doesn’t receive power at all. At this point, turning the car key doesn’t activate accessory power or crank up the engine, including switching on interior lights.

Closely examine the cable to determine the problem. As much as the battery cables have a simple purpose, they are a vital component of the electrical system. Any problem with the cables directly affects the vehicle.

Damaged or frayed battery cable

A good battery should be smooth with no corrosion or nicks. Any signs of fraying or damage affect the performance of the cable. Replace the cables as they are cheap, so that shouldn’t be an issue.

How Do You Diagnose the Bad Battery Cables?

Battery cables provide the needed cranking power and power your vehicle’s electronics or accessories when the engine is not running. The cables complete the alternator circuit when the engine is running. Therefore, corroded wires or a poor connection can cause car starting problems. Quick diagnosis is needed.

Electrical issues are harder to detect than physical issues. It’s not like you can examine the battery cable and tell if there is an electrical fault. For instance, if the battery wire gets too hot during cranking, probably it’s because it has a hidden defect or the cable is undersized.

However, there are diagnostic tests you can run to be sure if the battery cable has problems. Doing diagnostics confirm which problems exist. Diagnostic tests include:

how to test battery cables

Voltage drop test

As a rule of thumb, test the voltage drop whenever you have electrical problems. The voltage should not fall below 0.5V, round trip, or during cranking. Use a multimeter on the voltage setting to measure the voltage drop.

To do this, but one part of the lead on the actual positive battery post and the other lead on your starter stud. Have a friend crank up the engine and take voltage recording during cranking. Repeat the test for the negative battery post. Not that we are not using the battery terminal, just the post.

Add the two voltage measurements from the positive battery post-reading and those of the negative battery post. The sum should be less than 0.5 volts. If your addition gives you a value greater than 0.5 volts then you have a bad battery cable, maybe both cables.

Corrosion test

Check the battery cable terminal ends for signs of corrosion. Use a multimeter to test the negative battery cable for resistance.

The best way to diagnose the problem is by pulling the cable wire and testing using an ohmmeter. You can also use extended tester cables and remove the ends from the starter and battery or other connectors. Keep the wire in place without connecting.

Examine the connectors

Dirty cable connections result in less crank power. Use a wire brush on the connectors to see if there is corrosion or dirt on both the engine block and battery. Do the same for the starter and other end connections. Dirt can stop current flow leading to low crank power. Low crank power causes car starting problems.

The engine needs sufficient cranking power to start. Insert the voltmeter at the cable, then check for excessive resistance and other sophisticated diagnostics. If you are still in doubt, replace the battery cable.

Corroded Battery Cables Symptoms

Can corroded battery terminals cause a car not to start? Yes. Corrosion eats away the battery cable, causing improper functioning. If the car cannot start, you will be going nowhere. Why? Because there is no electricity flowing to the starter, hence no crank power to start the engine. Once the damage is extensive, the only solution is to replace the battery cable.

Chemical reactions in the battery are what cause corrosion. The byproduct of the reactions is corrosion, which can build up on the battery terminal and affect the battery cable terminal ends. Corrosion buildup over time, which can have severe consequences. How do you know if you have bad battery cables? Check for signs of corrosion.

  • Early signs of corrosion include white substance forming on the battery cable terminal end.
  • The cable terminal end ate away. With time if the white substances are not removed, they eat away part of the battery cable terminal end and you have a bad battery terminal.
  • A large lump of brown substances on the battery terminal ends. Common when you don’t clean the terminal for a long time. More deposits from the leaking electrolyte and reaction with other elements cause a buildup of corrosion on the cable terminal ends and battery terminals.
  • The battery cable snaps or is brittle. Happens when the cable is excessively corroded. The corrosion has made its way inside the insulation and hardened on the metal parts, including the cable terminal end.
  • Hot battery cable. Corrosion increases resistance generating more heat. This heats up the negative battery cable. The only remedy is to replace the battery cable.

How To Fix the Bad Battery Cables

The battery cables are the last components in the vehicle’s electrical circuit. Electricity flows through the cable to power your electrical system. Any problem with the battery cable can cause voltage loss and no electricity flow to all electrical systems of your car.

Without electrical power, the vehicle can’t start and all your electrical systems stop working. Your priority is to fix the bad battery cables to restore the smooth flow of electricity. Clean battery corrosion frequently to protect your terminals.

Use anti-corrosion protection

The best way to fix a bad battery cable if to prevent a recurrence of the problem using preventive measures. Use a spray battery protector which you can get in any auto parts store. The product prevents the buildup of corrosion on the battery cables and terminals. Clean the bad battery terminals before application and use is as per the manufacturer’s directions.

You can also apply anti-corrosion gel directly to the terminals. Don’t use it on the connectors. The gel prevents corrosion buildup, which translates to better performance and less cleaning.

Alternatively, you can install felt terminal protectors, if you don’t like dealing with the spray or gel. The protectors are affordable and easy to install on the terminals. The protectors have corrosion preventative saturation that doesn’t evaporate or dry and gives you long-term protection.

Replace the battery cable

A bad battery cable makes it difficult to start the car or the vehicle can stall unexpectedly and fail to start. Sometimes the battery can corrode or break. Don’t attempt to repair a broken battery cable or corroded cable. However, you can fix a bad cable terminal end. Learn how to replace battery cables.

Follow the steps below to replace your bad battery cable, but first get the right tools e.g. a wrench, screwdriver, socket, and ratchet.

Step 1

Use a screwdriver or wrench to remove both battery cables from your car battery. Remove the negative cable last to prevent shock accidents.

Step 2

Trace the negative cable to where it meets your chassis, then trace the positive battery cable to where it meets your car fuse block.

Step 3

Loosen the negative groundnut with a socket and ratchet, then remove the grounding wire. Inspect it to ensure it’s clean. Also, remove the nut holding the positive cable to your vehicle fuse block, then pull the cable off.

Step 4

Replace the positive cable with a new one on the fuse block, then tighten the cable down snugly. Also, put the new negative grounding cable on the chassis ground then tighten the nut.

Step 5

Run the new negative cable like before and place it on the negative battery terminal. Use a wrench to tighten the terminal end. Also, slide the positive cable over the positive terminal to attach it to the battery. Use a wrench to tighten the terminal end, then reattach your negative terminal and tighten until it snug.

Step 6

Insert the car key to start your vehicle to confirm you have a good connection.

What Happens When A Battery Cable Fails YouTube

Frequently Asked Questions (FAQs)

Q: What Does the Negative Battery Cable Do?

Ans: The negative battery cable provides grounding for all electrical components of the vehicle. The cable is black and has a negative (-) sign on it. Besides, it has a large cable with at least one smaller wire branching out. The negative battery cable is bolted with a nut to the vehicle’s engine block.

The smaller wires branching out are all attached to your chassis and offer a return path for the electrical components and lighting system of the vehicle. The return path enables the car to start, and if there is corrosion, the engine cannot start.

Q: Can a Bad Battery Cable Cause a Car To Stall?

Ans: Yes. If the battery cable is loose, broken, or corroded, there is an insufficient current flow to the ignition system of your vehicle making the car stall. Low crank power prevents the car from starting. Corroded terminal ends also affect the flow of electricity from the battery to the electrical system of your vehicle.

Q: How Often Do Battery Cables Need To Be Replaced?

Ans: You should replace the battery cable every 50,000 to 100,000 miles. These cables are frequently used by the vehicle, which makes them wear out easily. Also, replace the battery cable the moment there is are signs of damage because the cables are difficult to repair.

The amount of current passing through the battery cables and terminals makes them prone to wear. The battery cable terminal end can last 50,000 to 100,000 miles before they wear out under normal use without corrosion or damage issues. In short, besides the cable breaking or getting damaged, you can replace your battery cables after driving for 50,000 miles. The cables will have run their full lifespan and will no longer provide high performance.

Q: How Can You Tell the Difference Between Positive and Negative Battery Cables?

Ans: Both the negative and positive battery cables are vital for the vehicle’s electrical system. The simplest way to tell the positive cable from the negative cable is by looking at their color. Positive battery cables are red and larger as they give power to the electrical system for starting the engine and other vehicle accessories.

Negative battery cables are black and smaller compared to the positive cable. negative battery cables act as the grounding system for the vehicle’s electrical system or components.

Alternatively, look at their function. The positive battery cable is the one moving from the positive battery terminal to your vehicle’s starter solenoid. The negative cable is the one moving from the negative terminal to the chassis of the vehicle.

Q: Why Do You Connect the Negative Cable To the Engine Block?

Ans: Because it provides a more direct return path. This allows better current flow with less voltage drop. The trick is similar to plugging your appliance directly into your power outlet instead of through an extension cord.

Also, the starter is already mounted on your engine and the direct current return path is via the engine. So, connecting the negative battery cable to the engine block reduces the available voltage at the ignition. Because of that, the high starting current must flow through the chassis ground connection. Direct connection to the negative terminal can cause sparks which can ignite the hydrogen gas from your car battery causing a loud boom.

Final Words

Have your battery cables inspected by a professional mechanic to ensure the problems are fixed effectively? Operating a car with damaged battery cables is difficult. The instability is frustrating, and you may not drive the vehicle at all until the cables are fixed.

As soon as you realize there is a problem with your battery cables, run diagnostics or contact an expert mechanic. The above-mentioned symptoms of bad battery cables help you narrow down the problem. Observe the mileage limit and replace your battery cables after every 50,000 to 100,0000 miles.

Older battery cables are more brittle and easily break, exposing the bare wires to corrosion elements which accelerate engine starting failure. Feel free to call or email if you have a question or need clarification.

Tito

Hi There, I am R. Hasan Tito, a mechanic, and owner of this website. My friend and I created this website to share our knowledge, expertise, and experience with our fellow mechanics' community and car users. I am a specialist and certified automotive mechanics (Both Heavy Commercial and Private Cars). I have been working as a mechanic for over fifteen years. I worked for a long time at Global Rebound Automotive companies (Toyota, TATA, BMW, Nissan, TVs, and Others ) as a Mechanic and Mechanics Supervisor.

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