Battery Cable


The positive cable is normally red and the negative cable is black. The positive cable fastens to the battery and the starter solenoid or relay. The negative cable fastens to ground on the engine block. Some manufacturers use a negative cable with no insulation. Sometimes the negative battery cable may have a body grounding wire to help assure that the vehicle's body is properly grounded.

Be sure that a replacement cable has sufficient slack to allow movement of the engine on its mount.

The ground cable (usually the negative) should be disconnected first. This is a good habit to follow whenever doing major repairs.

  • Loosen the battery negative terminal clamp.
    • Spring-type cable connectors are removed by squeezing the ends of their prongs together with wide-jaw, vise-gripping, channel lock, or battery pliers. This pressure expands the connector so it can be lifted off the terminal post.
    • For connectors tightened with nuts and bolts, loosen the nut using a box wrench or cable clamp pliers. Using ordinary pliers or an open-end wrench can cause problems. These tools might slip off under pressure with enough force to break the cell cover or damage the casing.
    • Always grip the cable while loosening the nut. This eliminated unnecessary pressure on the terminal post that could break it or loosen its mounting in the battery.
  • Use a terminal clamp puller to remove the negative cable. Prying with a screwdriver or a bar strains the terminal post and the plates attached to it. This can break the cell cover or pop the plates loose from the terminal post.
  • Track the cable to its end and unbolt it from there.
  • Loosen the battery positive terminal clamp.
  • Use a terminal clamp puller to remove the positive clamp.
  • Track this cable to the starter relay or solenoid switch and unbolt it from there.
  • After servicing the cables or battery, install the positive battery cable by reversing the procedure to disconnect it. then install the negative cable. do not overtighten any nuts or bolts since this could damage the post or connector. before attempting to reinstall the old terminal clamp, clean the terminal clamps and enlarge their holes using expanding pliers.
Never reverse the polarity of the battery connection. Generally, all vehicles use a negative ground. Reversing this polarity damages the generator and circuit wiring.
  • Coat the terminals with corrosion preventative spray, then check the job by starting the car. You can also coat the connectors with petroleum jelly or battery anticorrosion paste.