my BMW 3 Series E90/E91 has an electrical issue causing the lights to flicker, what to do?

Solution

1. Preparation

• Tools Required: OBD-II scanner, multimeter, socket set, wrench set.
• Disconnect the negative terminal of the battery to prevent electrical shorts during repair.

2. Battery Inspection and Cleaning

• Check the battery terminals for corrosion.
• Clean the terminals using a wire brush and a mixture of baking soda and water to neutralize any acid.
• Reconnect the terminals securely, ensuring they are tight.

3. Alternator Testing and Replacement (if needed)

• If the alternator voltage output is below the normal range, remove the alternator:
  • Disconnect the battery (negative terminal).
  • Remove the serpentine belt using a belt tensioner tool.
  • Disconnect the electrical connectors from the alternator.
  • Unscrew the mounting bolts and carefully remove the alternator.
• Replace with a new or refurbished alternator if it is faulty.

4. Wiring Inspection

• With the battery disconnected, inspect the wiring harness for any visible damage or fraying.
• Repair any damaged wiring with appropriate connectors and heat-shrink tubing.

5. Reassembly and Final Checks

• Reconnect all components and ensure all screws and bolts are securely tightened.
• Reconnect the negative battery terminal.
• Start the vehicle and check for proper operation of the lights and electrical system.