how to fix the defroster on my BMW 3 Series E90/E91 (2005-2012)?

Solution

1. Preparation

• Gather all necessary tools and parts.
• Disconnect the negative battery terminal to ensure safety during repairs.
• Allow the vehicle to cool down if it has been running.

2. Replace Cabin Air Filter

• Tools Required: Flathead screwdriver, socket set (if needed for cover removal).
• Remove any covers or panels obstructing access to the cabin air filter.
• Locate the cabin air filter housing, typically found behind the glove compartment.
• Remove the old cabin air filter and replace it with a new one, ensuring it is oriented correctly.

3. Inspect and Replace Blower Motor (if faulty)

• Tools Required: Socket set, multimeter.
• Access the blower motor, usually located under the dashboard on the passenger side.
• Using a multimeter, check for voltage at the blower motor connector.
• If no voltage is present, trace back to the blower motor resistor or switch for faults.
• If the blower motor is faulty, disconnect it, remove the mounting screws, and replace it with a new motor.

4. Check and Replace Temperature Blend Door Actuator (if necessary)

• Tools Required: Torx or socket set.
• Access the actuator, typically located behind the dashboard near the HVAC unit.
• Disconnect the actuator from its electrical connector.
• Manually check if the blend door moves freely.
• Replace the actuator if it does not respond to commands or is stuck.

5. Recharge AC System (if refrigerant is low)

• Tools Required: AC manifold gauge set, refrigerant.
• Connect the AC manifold gauge to the low and high-pressure ports of the AC system.
• Start the engine and turn on the AC to the maximum setting.
• Check the pressure readings and recharge the system with the appropriate refrigerant type if necessary.