Why is there no hot air when the car heater is on?
2 Answers
Air conditioning heating without hot air is caused by a malfunction in the heater core or possibly a fault in the heater core's water valve. When this occurs, it is necessary to inspect both the heater core and the heater valve. Car air conditioning heating utilizes the engine's heat. During heating, the engine's high-temperature coolant flows through the heater core, and the air blown by the blower also passes through the heater core, allowing the car's air conditioning vents to emit warm air. The car air conditioning system, referred to as car AC, is used to adjust and control the temperature, humidity, air cleanliness, and airflow within the car's cabin to an optimal state. It provides a comfortable riding environment for passengers, reduces travel fatigue, creates good working conditions for the driver, and plays an important role in ensuring safe driving as a ventilation device.
Over the years of repairing air conditioners, the most common reasons I've encountered for no hot air in winter are as follows. First, the air conditioner isn't set to heating mode—many people still use cooling mode in winter. Second, the temperature is set too low; it needs to be higher than room temperature to produce hot air. Third, the outdoor unit is frozen or the outside temperature is too low—many air conditioners stop working when it's below -5°C. Fourth, the filter is completely clogged with thick dust, blocking the airflow. Fifth, lack of refrigerant or a stuck four-way valve, which can be troublesome to fix. There's also a special case where the anti-cold air function delays airflow when first turned on—wait 3-5 minutes for it to normalize. If none of these checks solve the problem, it might be a motherboard or sensor issue, requiring a professional technician to disassemble and inspect.
