why does my BMW 3 Series E90/E91 (2005-2012) AC blow hot air instead of cold

Solution

1. Preparation

• Gather tools and parts needed for the repair.
• Disconnect the battery to ensure safety while working on the electrical components.

2. Recharge Refrigerant

• Tools Required: AC refrigerant kit, pressure gauge.
• Using the pressure gauge, check the low and high side pressures of the AC system.
• If low, attach the refrigerant canister to the low-pressure service port and recharge the system according to manufacturer specifications.

3. Replace AC Compressor (if necessary)

• Tools Required: Socket set, wrench set, AC compressor replacement kit, torque wrench.
• Remove the drive belt by loosening the tensioner pulley.
• Unbolt the AC compressor from its mounting brackets.
• Disconnect electrical connectors and refrigerant lines (ensure all refrigerant is evacuated before this step).
• Install the new AC compressor in reverse order, ensuring proper torque specifications are followed.

4. Inspect and Replace AC Expansion Valve or Receiver-Drier

• Tools Required: Wrench set, socket set.
• Locate and remove the receiver-drier or expansion valve as applicable.
• Replace with a new part, ensuring all seals are replaced to prevent leaks.

5. Recharge System and Test

• After repairs, evacuate the system using a vacuum pump for at least 30 minutes.
• Recharge the system with the appropriate amount of refrigerant.
• Reconnect the battery and start the vehicle, then turn on the AC to test if cold air is produced.