A corroded battery terminal can be the cause of a lot of problems and often times it is overlooked when your vehicle won't start. By replacing your terminals instead of buying a new battery you could save a fair amount of money and prevent future engine problems. So how do you know if the problem is your battery, the terminals or another problem like a bad starter? First inspect the battery terminals, located on the end of your battery cables that connect the vehicle to the battery itself. If they are corroded and covered in a discolored, sand like substance then they could be the cause of your problem. Prior to beginning it is important to know that your battery is fully charged and in working order. A bad battery could be the cause of your problems so it is a good idea to eliminate that option prior to removing your terminals. That being said it is never a bad idea to clean, or even replace, your terminals.
Remove the terminals from the battery, starting with the negative post (the black one) then the positive post (the red one). If necessary remove the battery so you have better access to cleaning it and the terminals inside the engine compartment.
Clean the battery posts and terminals. To do so wet the posts and terminals with water. Once wet sprinkle baking soda over them and scrub any corrosive material with a metal wire brush. Any discoloration or clumpy sand like substance should be removed. The metal of each post and terminal should be shiny when completed. Sometimes cleaning the posts will alleviate all of your problems and it is often a good idea to test the engine to see how it starts after this step.
With the cables disconnected sever the cable wire near the corroded terminal using a hacksaw or wire cutter.
Inspect the wires for corrosion or damage. Bad wires are sometimes to blame in addition to terminals. If the wires are corroded make sure you trim them back, removing the corrosion, before you connect new terminals. It is important to make sure the wire has enough length to reach the battery though. Remove roughly one inch or wire insulation prior to installing new terminals.
Remove the retainer screws on your new terminals and insert the wires into the appropriate location. Tighten the screws once the terminals are place. Repeat the process for the second terminal.
Reconnect the terminals to the battery and start the car. Hopefully this will alleviate your engine problems.
Replacing corroded or bad battery terminals is an easy process that requires minimal tools and expertise. Some mechanics even advise to routinely clean your terminals as a regular part of your vehicle maintenance schedule in 6 months intervals for optimal performance.