why does my Volkswagen Tiguan First Generation (2007-2018) battery die overnight when the car is off

Solution

1. Preparation

• Tools Required: Multimeter, battery load tester, socket set, wire strippers, electrical tape.
• Disconnect the negative battery terminal to prevent electrical shocks during inspection.

2. Perform a Battery Load Test

• Connect the load tester to the battery terminals.
• Apply a load according to the tester’s instructions (typically ½ of the battery's CCA rating) for 10-15 seconds.
• Observe the voltage; a reading below 9.6 volts indicates a weak battery needing replacement.

3. Check for Parasitic Draw

• Reconnect the negative battery terminal.
• Set the multimeter to measure current (amps) and connect it in series with the battery terminal and cable.
• Record the reading; anything above 50 mA indicates excessive draw.
• Remove fuses one at a time to identify which circuit is causing the draw.

4. Inspect and Repair Faulty Components

• Once the problematic circuit is identified, check all components connected to that circuit.
• Repair or replace any faulty components (e.g., a malfunctioning radio, alarm system).
• Ensure all connections are secure and free of corrosion.

5. Reassemble and Test

• Reinstall any removed fuses and reconnect all components.
• Reconnect the negative terminal to the battery.
• Start the vehicle and measure the voltage at the battery while the engine is running; it should be between 13.7 to 14.7 volts.