Why is there no warm air from the car air conditioner?

[KalebMarie]

The reasons for no warm air from the car air conditioner are: 1. Engine cooling system failure; 2. Incorrect position of the warm air baffle; 3. Lack of antifreeze; 4. Failure of the heat dissipation circulation system. The method to turn on the warm air in a car air conditioner is: 1. After starting the vehicle, turn off the AC button; 2. Wait until the water temperature rises to the normal value, then turn on the warm air. The car air conditioner, also known as the car air conditioning device, is used to adjust and control the temperature, humidity, air cleanliness, and air flow inside the car cabin to an optimal state. Its functions are: 1. To provide a comfortable riding environment for passengers and reduce travel fatigue; 2. To create good working conditions for the driver.

[LaSawyer]

Last winter when I drove out, I encountered this issue and was shivering from the cold. Later, I figured out it was a fault in the heating system - most commonly caused by insufficient coolant or airlocks, which affects heat transfer to the cabin. Clogging of the heater core by scale deposits is also frequent, especially in older cars. I've also experienced situations where the heater blend door inside the dashboard gets stuck - it switches to cool air smoothly in summer but gets jammed in the cold air position during winter. By the way, turning on the heater immediately after starting the car definitely won't work; you need to wait until the coolant temperature reaches around 90 degrees. During the last maintenance, the mechanic mentioned that if the two heater hoses show inconsistent temperatures, it basically confirms the heater core is clogged.

[JayceRose]

Having driven a taxi for thirty years, I've seen plenty of heating issues. First, feel the temperature of the two heater hoses in the engine bay. If both are cold, it means hot water isn't circulating, likely due to a thermostat stuck open. If one is hot and the other cold, there's an 80% chance the heater core is clogged. Here's a simple test: start the car, turn on the heater, and pop the hood to listen for the blower's whirring sound. Just the other day, I picked up a young guy who'd installed the thermostat backwards while replacing it himself, causing the heater to stop working entirely. Nowadays, many cars use electric motors to control the blend door, and if that fails, it can also result in only cold air coming from the vents.

[SanKaden]

My friend just bought a used car and ran into this issue. If the heater isn't blowing hot air, first check if the coolant temperature gauge has reached the midline. If the temperature doesn't rise after driving for half an hour, inspect whether the thermostat has failed. If the antifreeze hasn't been changed in five years, it might have turned into sludge and clogged the heater core. For those who've modified their car audio, be aware that if the air conditioning ducts were tampered with during dashboard removal, the heater flap linkage might have been installed incorrectly. A certain German car's heater control valve is particularly prone to failure, and repairing it requires removing the entire dashboard. Remember to turn off the AC button when using the heater in winter, otherwise the compressor will keep running unnecessarily. If the antifreeze appears cloudy or discolored, replace it immediately.