Car Not Heating? Here Are the Possible Causes

Car Not Heating

When the temperature falls below freezing, not having a working heater can be more than just uncomfortable, it can also be hazardous if fog and ice build up on the windows, limiting visibility.

How Your Car's Heater Works

Once your car has been running for a little while, heat from the engine is transfered to the coolant. This hot coolant is sent to a small radiator called a heater core. Fans then blow the hot air generated by the heater core throughout the vehicle's interior.

Depending on the outside temperature, it usually takes between 5 to 10 minutes for the engine to warm up enough to give the heater core enough usable heat. If it's below zero you make have to wait even longer.

Thermostat Problems

An engine's thermostat controls the flow of coolant. When the temperature is cold, the thermostat restricts the flow of coolant out of the engine to allow it to warm up more quickly. Once it warms up, more coolant is released to flow between the radiator and the engine, allowing the temperature to remain inside the optimal range.

By design, when a thermostat fails, it's going to be stuck in the open position. This prevents the engine from overheating by ensuring that the hot coolant is not trapped in the engine, instead allowing it to flow freely to the radiator. This also means the coolant is going be constantly cooled, leaving little heat available for the heater core to provide to warmth the interior of the car. Leaking coolant can also limit the amount of coolant that reaches the heater core.

Heater Core Problems

When the heater core becomes dirty, it becomes less efficient. Flushing the lines with water can remove the grime blocking the flow of coolant.

To determine if the heater core has failed, your mechanic will need to troubleshoot the entire system to eliminate other potential issues. This includes testing fuses, heater switches, blower motors and other components.

Is your car's heater blowing cold air? Call Parkway Auto Care. We can quickly diagnose the cause and get the heat blowing again.


Parkway Auto Care
1581 Ford Pky St Paul, MN 55116

Phone: 651.698.3208
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We are a NAPA AutoCare Center in St Paul Minnesota, providing the following services:


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7:00 AM - 6:00 PM

8:00 AM - 1:00 PM

Closed Sunday

NAPA St. Paul MN

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