how to fix the defroster not working in my BMW 3 Series E90/E91?

Solution

1. Preparation

• Gather the necessary tools and parts.
• Disconnect the vehicle's battery to ensure safety during repairs.

2. Inspect and Replace the Cabin Air Filter

• Tools Required: Screwdriver, replacement cabin air filter.
• Remove the cover for the cabin air filter located under the dashboard or behind the glove box.
• Take out the old cabin air filter and inspect for dirt or blockage.
• Install the new cabin air filter according to the airflow direction indicated on the filter.

3. Check and Replace Blower Motor

• Tools Required: Socket set, multimeter, replacement blower motor (if faulty).
• Access the blower motor, typically located under the dashboard on the passenger side.
• Disconnect the electrical connector and remove the mounting screws.
• Test the blower motor with a multimeter to check resistance; replace if it shows no continuity.
• Install the new blower motor and reconnect the electrical connector.

4. Inspect and Repair or Replace Heater Core

• Tools Required: Socket set, coolant catch pan, replacement heater core (if necessary).
• Drain the coolant from the radiator using the drain valve.
• Disconnect the heater core hoses from the engine compartment.
• Remove the dashboard to access the heater core (may require multiple disconnections and careful handling).
• Inspect the heater core for leaks or blockages; replace if necessary.
• Reassemble in reverse order and refill the cooling system with appropriate coolant.

5. Test the HVAC System

• Reconnect the vehicle's battery.
• Start the engine and set the climate control system to defrost mode.
• Monitor operation to ensure the defroster is functioning correctly.