A car's heater does not generate heat if the coolant level is low or restricted by buildup, if the water pump failed or if the thermostat is broken. The heater fan is also sometimes an issue.Know More
According to the Popular Mechanics website, a common cause of a car's heater not working is a buildup in the heater core. Grime or other sediment accumulate in the core and restrict the flow of heated coolant that serves as the source for the heater. The coolant needs to be flushed and replaced. This problem also occurs if the coolant is low, in which case it needs to be topped off.
Another possible problem is the thermostat. The thermostat controls a thermal valve that opens when the engine gets hot and closes when it gets cold. If the thermostat is worn out or broken, the thermal valve might remain open, which does not allow the coolant to warm up enough to provide heat for the heater. The thermostat then needs replacing. This problem also occurs if the water pump fails, in which case the car also overheats.
If the heater core is functioning properly but only a trickle of heat is coming from the vents, the problem might be the heater fan. Either the fuses for the fan or the whole fan might need replacing.Learn More
Removing the thermostat from a vehicle causes the engine to operate at a cooler temperature than its design. While this prevents overheating, it also increases fuel consumption, the viscosity of motor oil and engine wear. If the ambient temperatures are cold, the vehicle's heating system sometimes does not provide enough heat to warm passengers or defrost windows in a timely manner.Full Answer >
The most common reasons a car's heater may stop working include too little coolant, a failed heater core or a faulty heater control air bend door. A coolant, such as antifreeze, is necessary for air to move through the heater core and into the car.Full Answer >
The most common cause of a heater blowing cold air is a bad thermostat. The thermostat opens and closes to regulate coolant flow. A thermostat typically opens when the coolant temperature is at 195 degrees Fahrenheit; if malfunctioning, it does not heat the coolant enough to blow hot air.Full Answer >
A car's heater blows cold air when the actuator or heater core is malfunctioning. The heater actuator is mounted on top of the heater core behind the engine.Full Answer >