Audi A4 heater blowing cold air despite reservoir filled with anti-freeze on Audi A4

Some Audi A4 owners report experiencing issues with their heater blowing cold air, even when the reservoir is filled with anti-freeze. These problems may stem from low coolant levels, which can hinder circulation through the heater core, or air trapped in the cooling system that affects heating performance. Additionally, a clogged heater core can restrict hot coolant flow, while a faulty thermostat may prevent the engine from reaching optimal temperatures, resulting in cold air from the vents. Some owners also report issues with the blend door actuator, which can misdirect airflow, and malfunctions in the HVAC control unit that compromise heating efficiency. To address these concerns, it is advisable for owners to seek a professional mechanic for a thorough inspection to identify and resolve the underlying issues.