There are several potential reasons why the air conditioning (A/C) in your 2012 VW Passat may stop blowing cold air and only blows warm air. Some common causes include:
Refrigerant leak: A refrigerant leak can cause the A/C system to lose its cooling capacity over time. When the refrigerant level drops below a certain point, the A/C will stop blowing cold air.
Faulty compressor: The A/C compressor is responsible for compressing the refrigerant and circulating it through the system. If the compressor is faulty or not engaging properly, it can result in warm air blowing from the vents.
Blocked or clogged condenser: The condenser is responsible for releasing heat from the refrigerant. If it becomes blocked or clogged with debris, it can hinder the A/C system's ability to cool the air.
Electrical issues: Various electrical components, such as sensors and switches, play a crucial role in the A/C system's operation. Malfunctioning electrical components can disrupt the cooling process.
Broken blend door or actuator: The blend door and actuator control the flow of air through the A/C and heating system. If they malfunction, the A/C may not be able to direct cold air into the cabin.
Low refrigerant pressure switch: Modern A/C systems have a low refrigerant pressure switch that prevents the compressor from running when the refrigerant level is too low to prevent damage to the compressor.
To diagnose the specific issue and perform the necessary repairs, it is advisable to take your VW Passat to a qualified mechanic or an authorized Volkswagen service center. They can perform a thorough inspection of the A/C system, identify the problem, and provide the appropriate solution to get your A/C blowing cold air again.