How to Replace a Negative Battery Cable

A negative battery cable must be replaced if it is corroded or loose. Battery cables will wear out over time due to weather elements and other factors such as frequent handling. Depending on your car make and model, you have to follow the appropriate instructions given by the manufacturer. Vehicles have different battery systems and layouts, so you must get a schematic/electrical wiring diagram to pinpoint the position of the negative cable. A negative battery cable can also be replaced when you are upgrading your car electrical system. You may need to remove such things as the stater solenoid as well. It is advisable to do this job in a garage or backyard working place.

A corroded or loose battery cable can create trouble in your vehicle. It will interfere with the normal functioning of the battery as well as your car engine. Your engine may fail to start and the battery may not charge properly. As a temporary measure, you can clean the corroded cable and re-install it onto the battery. Use sandpaper for this purpose, then clean with a cloth. This might be all you need to fix your cable if the corrosion or damage is not too bad. If the corrosion is too deep, then you should replace the cable.

Tools and Materials Needed:

  • Battery cable
  • wrench

Step 1 – Switch off Power

Start by cutting off the power in your vehicle. Find out if your vehicle’s battery system is connected to a security alarm. Some vehicles will set off an alarm if the battery cables are disconnected. It might be hard to stop the alarm if you do not have a special key or code to disable it. You must therefore get all the codes and keys before removing the cables.

When removing battery cables, it is normal practice to begin with the negative terminal also known as the earth. This is a safety precaution to prevent any accidental short circuits. The black cable is the negative terminal and the red cable is the positive terminal. However, double-check with your car manual to make sure you are removing the right cable.

Step 2 – Open the Car Hood

Pull up the car hood and then lock it in position once it’s fully open. Make sure you are working within a walled garage, to avoid strong winds.

Step 3 – Find the Battery

Using your car wiring diagram, locate the battery. It is usually located under the passenger seat.

Step 4 – Find the Negative Cable

Identify the negative cable (it is usually black in color). Using a wrench, remove the bolt that holds the cable. Turn the wrench anti-clockwise until the bolt is loose.

Step 5 - Remove Negative Cable

Pull out the negative cable from the battery terminal.

Step 6 – Locate where the Cable is Grounded

Referring to your car wiring diagram, identify where the cable terminates in the engine box. The negative battery cable usually terminates at the well of the car wheel.

Step 7 – Remove Nuts

Using a wrench, remove the nuts holding the end of cable in the engine box at the wheel well. Turn the nut anti-clockwise until it’s loose.

Step 8 – Remove Negative Cable

Pull out the old cable from the bolts and put it aside.

Step 9 – Fix New Negative Cable

Attach one end of the new cable to the negative battery terminal and the other end to the wheel well into the bolt holes. Screw on the nut and turn it clockwise using a wrench, until it feels tight.