One of the most common reasons for a cold car heater is a low coolant level. Coolant, also known as antifreeze, plays a crucial role in maintaining the right temperature inside your engine and heating system. When the coolant level is low, there may not be enough warm coolant circulating through the heater core, resulting in cold air blowing from the vents. To resolve this issue, check your coolant reservoir and top it off if necessary. Be sure to use the manufacturer-recommended coolant mixture for your vehicle.

Modern vehicles often use blend door actuators to control the blend of hot and cold air in the HVAC system. If the blend door actuator malfunctions, it may get stuck in the cold air position, causing your heater to blow cold air. Replacing the faulty actuator can solve this problem.