1. Check the obvious:
* Battery Terminals: Clean the battery terminals and cable connections. Corrosion can prevent a good electrical connection, even if the battery itself is fine. Use a wire brush and baking soda/water solution to clean them thoroughly.
* Battery itself: Have the battery tested at an auto parts store. Even if it holds a charge temporarily, it might be internally damaged and unable to accept a charge properly.
2. Test the charging system:
* Voltage at the battery: With the engine running, a voltmeter should show between 13.5 and 14.5 volts at the battery terminals. Anything significantly lower indicates a charging problem.
* Alternator: The alternator is the most likely culprit. A failing alternator won't produce sufficient voltage to charge the battery. A mechanic can test the alternator output directly.
* Voltage Regulator: The voltage regulator controls the alternator's output. A faulty regulator can cause overcharging or undercharging. It's often integrated into the alternator on newer vehicles, but some older ones have a separate regulator.
* Wiring: Check the wiring between the alternator, battery, and voltage regulator for any breaks, shorts, or loose connections. This can be tricky and requires some electrical knowledge.
* Battery cables: Even if the terminals are clean, the cables themselves may be corroded internally or damaged. Visually inspect them closely.
3. If you're not comfortable working on the car yourself:
Take your DeVille to a mechanic or auto repair shop. They have the tools and expertise to properly diagnose the problem and repair it. Describing the symptoms (battery won't hold a charge even after charging) will help them narrow down the possibilities.
Important Note: Working with a car's electrical system can be dangerous. If you're unsure about any step, it's best to consult a professional.
