There could be several reasons why your 2019 Audi A4's air conditioning is not blowing cold air. Let's explore some potential causes and solutions:

 
Check the Refrigerant Levels
 

• Ensure that the air conditioning system has sufficient refrigerant. Low refrigerant levels can cause the system to blow warm air instead of cold. This could be due to a leak in the system. Therefore, it's essential to have a professional check the refrigerant levels and refill or repair any leaks if necessary.

 
Inspect the AC Compressor
 

• The AC compressor is a critical component that compresses the refrigerant and circulates it through the system. If the compressor isn't working properly, it may not be able to deliver cold air. Listen for unusual noises from the compressor and have a technician inspect it for any malfunctions or damage.

 
Examine the Condenser and Condenser Fan
 

• Located at the front of the vehicle, the condenser receives refrigerant from the compressor and helps to cool it down. If the condenser is blocked by debris or the condenser fan is not working correctly, the air conditioning system may not blow cold air. Check for any visible blockages and confirm that the fan is running when the AC is on.

 
Assess the HVAC Control Module and System Settings
 

• Sometimes the problem might lie within the HVAC control module or incorrect system settings. Ensure that the settings are correctly adjusted for cold air. If the control module is malfunctioning, it might need to be reset or replaced.

 
Look at the Cabin Air Filter
 

• A clogged or dirty cabin air filter can restrict airflow and reduce the effectiveness of the air conditioning system. Inspect the filter and replace it if it's dirty or clogged to allow for better airflow and cooler air.

 
Check for Electrical Issues
 

• The air conditioning system relies on several electrical components and connections. Blown fuses, faulty wiring, or failing sensors can prevent the system from functioning optimally. Consider having an automotive electrical specialist inspect the system to identify and fix any electrical issues.

 
Inspect the Blower Motor
 

• If the blower motor isn't functioning correctly, it may not provide adequate airflow through the air conditioning system. This could result in a lack of cold air being distributed inside the car. Listen for any strange noises from the blower motor and have it checked by a professional if necessary.

Diagnosing and repairing issues with your car's air conditioning system can sometimes require specialized skills and equipment, so it's advisable to consult a certified mechanic or an Audi dealership for a thorough inspection and service.