my Volkswagen Tiguan First Generation (2007-2018) battery keeps dying overnight, what’s wrong?

Solution

1. Preparation

• Tools Required:
  • OBD-II scanner
  • Multimeter
  • Socket set
  • Wrench set
• Disconnect the negative terminal of the battery to ensure safety during testing and repairs.

2. Clean and Secure Battery Connections

• Sub-steps:
  1. Inspect the battery terminals for corrosion; if present, clean with a terminal cleaner or a mixture of baking soda and water.
  2. Tighten the battery terminal bolts using the appropriate socket or wrench.
  3. Reconnect the negative terminal and ensure it is secured properly.

3. Test and Replace Battery

• Sub-steps:
  1. If the battery voltage is low, charge the battery using a battery charger according to the manufacturer's instructions.
  2. If the battery is more than 3-5 years old or fails the load test, replace it with a new battery of the same specifications (typically Group 48 for Tiguan).
  3. Properly dispose of the old battery following local regulations.

4. Check and Replace Alternator (if needed)

• Sub-steps:
  1. If the alternator is not producing the correct voltage, remove the serpentine belt using a wrench to relieve tension on the tensioner.
  2. Disconnect the alternator wiring harness and remove the mounting bolts.
  3. Replace the alternator with a new or remanufactured unit, tightening bolts to manufacturer specifications.
  4. Reconnect the wiring harness and reattach the serpentine belt.

5. Address Parasitic Draw (if found)

• Sub-steps:
  1. If a parasitic draw is detected, remove fuses one by one while monitoring the current draw with the multimeter.
  2. Identify the circuit causing the draw and inspect associated components (e.g., lights, modules).
  3. Repair or replace faulty components as necessary.