Modern electrical systems put big demands on a vehicle's battery. Sometimes a battery will fail with no warning, but usually the first sign of trouble is that the engine is hard to start when cold (the starter motor turns more slowly than usual). This is then followed by a complete failure to start.
There are three main reasons for a battery to go dead. One is age, in which case replacing the battery will cure the problem. The second is leaving the lights on (or even the radio or alarm, if parked for a long time); generally a jump-start will solve the problem - although the life of the battery will be shorter following a complete discharge. The third is a problem with the charging system; replacing the battery won't cure that.
A Haynes Repair Manual gives simple tests so that you can identify the reason for your dead battery.
Once you've decided the battery needs to be replaced, you'll need a new battery of the correct size and capacity to fit your vehicle. While you’re at the parts store, pick up some anti-corrosion spray to put on the battery terminals and a "memory saver." This simple device, run by a small battery, will keep you from losing the presets for electronic components (like the radio) when the battery is disconnected.
Disconnect the cables from the old battery, negative first (look for a '-' sign near the battery terminal). Loosen the clamp nut or bolt - details vary by vehicle - and lift out the battery. Be careful not to drop it, and keep it upright to avoid acid spillage.
Install the new battery, secure it with the clamp and connect the cables, negative last. Protect the terminals against corrosion by spraying them with anti-corrosion spray.
Check that the negative cable connection to the vehicle body is clean and tight. Unbolt it and clean it with a wire brush, if necessary.
- A loose or broken alternator drivebelt can cause thebattery to go dead.
- Most modern batteries are sealed for life, so you can no longer check the electrolyte level.
- If you find your battery charge is frequently low due to short trips or long periods of inoperation, an inexpensive “trickle charger” from an auto parts store can keep it fully charged.
- Dispose of the old battery responsibly. The lead in thebattery can be recycled.
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