my Volkswagen Golf MK7 (2015-2019) battery drains overnight, what could be the cause?

Solution

1. Preparation

• Gather tools: multimeter, socket set, screwdriver set, and battery terminal cleaner.
• Ensure all electrical systems are off and the vehicle is parked safely.

2. Disconnect Battery

• Use a socket set to remove the negative terminal from the battery.
• If necessary, remove the positive terminal as well for safety.

3. Identify and Repair Faulty Component

• If a fuse is identified as the cause of the draw:
  • Remove the associated component and inspect for shorts or damage.
  • Repair or replace the faulty component as needed.
• If the alternator is not charging correctly:
  • Remove the alternator belt and disconnect the alternator.
  • Test the alternator with the multimeter and replace it if output is outside the normal range.

4. Reconnect and Test

• Reconnect the battery terminals, ensuring they are clean and tight.
• Start the vehicle and measure the battery voltage; it should increase to 13.5V - 14.5V.
• Allow the vehicle to run for a few minutes and check for any abnormal electrical behavior.

5. Final Check

• Close the hood and ensure all tools are removed from the engine bay.
• Perform a test drive to ensure no warning lights remain illuminated.