Cleaning and Replacing Car Battery Terminals

corroded car battery terminal
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  • Beginner

Many avid car enthusiasts take good care of their vehicles, regularly washing and waxing them. Unfortunately, this attention to detail doesn’t always extend to the car’s internal vital components, like the battery cables and terminals. You can save yourself a headache if you check your battery cables and terminals on a regular basis to see if they are loose or corroded. Follow these few steps to maintain these vital internal parts and correct issues before they’re too big to fix from home.

Step 1 – Inspect and Clean Top-Post Terminals

Battery terminals should be inspected and cleaned twice per year, and if the cable terminals are corroded, they should be replaced. You don't have to hire a professional auto mechanic to complete these easy tasks.

Remove Terminal Caps

When the engine is off, begin by removing terminal caps, if necessary, and disconnect the negative battery cable. The negative battery cable is black, and it will be marked with a minus sign or an abbreviation.

Then, loosen the retaining nut with a wrench and twist the connection backward and forward while pulling it upward to remove it. If the terminal won't come off, tap it lightly with a small hammer or pull it off with a cable-terminal puller. Once the negative cable has been removed, disconnect the positive cable using the same method.

Clean the Posts

Carefully clean the battery posts and cable terminals with a small wire brush or terminal cleaning tool. Clean both the inside and the outside until the metal appears to be clean and free from corrosion. Then, dust them with a small paintbrush to remove any loose corrosion. If the cable terminals are in good condition, securely reconnect them and repeat the inspecting and cleaning process in six months.

If they are especially corroded, you can try cleaning them with a small amount of baking soda and vinegar mixture. If that doesn't work, you might need to replace them. You can do so by following the directions in the “Replacing Terminals” section below.

Step 2 – Inspect and Clean Side Terminals

Depending on the position of the battery, the side terminals are usually easier to remove. Following the same instructions for cleaning top-post terminals, use a wrench to take off the negative retaining bolt first, and then remove the cable. Do the same on the positive side. Even if the round contacts don't appear corroded, take the time to clean them with a small wire brush or terminal cleaning tool, and clean corrosion dust with a small paintbrush. After cleaning, securely reconnect the terminals, or if they’re too badly corroded, it's time to replace them.

Step 3 – Replace Terminals if Needed

Sever Cables

If the cable terminals appear badly deteriorated by corrosion, or if the jaws of top terminals are able to touch, they should be replaced. While the cables are disconnected, sever the cable wire near the corroded terminal using a hacksaw or a wire cutter. Check the wire for corrosion as well, and if it's severely corroded, trim away the deteriorated wire. Make sure the wire can still reach the battery after trimming. If too much of the wire must be trimmed away, you must replace the cable. Before reconnecting any cables, strip off about 1 inch of wire insulation.

Install New Terminal

To install a new terminal, remove the retainer screws and insert the wire in the appropriate location beneath. Put the terminal back together and tighten the screws. Complete the process on the other side if necessary, and check and clean them again in six months for optimum starting and dependable operation.