my Volkswagen Tiguan First Generation (2007-2018) has a weak battery after a full charge

Solution

1. Preparation

• Gather tools: multimeter, OBD-II scanner, battery load tester, wrench set, wire brush, battery terminal cleaner.
• Ensure the vehicle is parked on a level surface with the engine turned off and cooled down.

2. Battery Cleaning

1. Disconnect the negative terminal first and then the positive terminal from the battery.
2. Inspect battery terminals for corrosion; if present, clean them using a wire brush and battery terminal cleaner.
3. Rinse any cleaning solution off with water and dry thoroughly.

3. Battery Replacement (if necessary)

1. If the load test shows the battery is weak, remove the battery by unbolting it from its tray.
2. Lift the battery out carefully; ensure it’s upright to avoid any acid spills.
3. Install the new battery in the reverse order of removal, ensuring it fits snugly.
4. Connect the positive terminal first, followed by the negative terminal, and secure them tightly.

4. Alternator Check

1. Start the engine and measure the voltage at the battery terminals.
2. It should read between 13.8V to 14.5V. If the voltage is lower, the alternator may need replacement.
3. If necessary, remove the alternator according to the manufacturer’s service manual and replace it with a new unit.

5. Reassemble and Test

1. Reconnect all electrical connections and ensure all components are secured.
2. Start the engine and observe if all electrical accessories function properly.
3. Check the battery voltage again to confirm proper charging during engine operation.