my BMW 3 Series E90/E91 (2005-2012) heater only blows cold air what could be wrong

Solution

1. Preparation

• Gather necessary tools and parts.
• Ensure the engine is cool to avoid burns.
• Disconnect the battery to prevent electrical issues during repair.

2. Check Coolant Level

• Open the hood and locate the coolant reservoir.
• If low, top off with a 50/50 mix of coolant and water.
• Start the engine and allow it to warm up, then check again.

3. Inspect and Address Leaks

• Visually inspect all hoses and connections for leaks.
• If leaks are found, replace damaged hoses or fittings as necessary.

4. Heater Core Inspection

• Locate the heater core hoses in the engine bay.
• Disconnect the hoses and check for blockages by flushing the heater core with water.
• If blocked, replace the heater core; if it’s clear, reattach the hoses securely.

5. Thermostat Replacement (if faulty)

• Drain the coolant to a manageable level.
• Remove the thermostat housing (typically requires a socket set).
• Replace the thermostat with a new one, ensuring it is oriented correctly.
• Refill the cooling system with the appropriate coolant mixture.

6. Climate Control Settings Reset

• Reconnect the battery.
• Turn on the ignition and reset the climate control system settings, if applicable.