Why is my car heater not blowing hot air?

Is the interior of your vehicle so cold you could store a snowman inside it? Your car heater may not be working. We’ll quickly show you how a heating system works and then explain why your car might not be blowing hot air.

How your car’s heating system works

Keeping a car comfortable takes many parts, any of which can break down through wear and tear or direct damage. These are the base components of the heating system in most vehicles:

• Coolant: This fluid is the same coolant used to remove heat from your engine.
• Heater hoses: These hoses carry the heated coolant to the heater core.
• Blower fans: Your car’s heating system has multiple blower fans to move air through it.
• Heater core: Comprising several components, this part adds heat to the coolant as required.
• Coolant shut-off valve: Not all vehicles have this part. It shuts off the flow of the coolant from the engine to the heater core when the heating system is not in use.
• Auxiliary coolant pump: This part is more commonly used in vehicles where the heating system is in the rear compartment. It assists with ensuring consistent hot air in the cabin.
• Blend door: Where heating and air-conditioning systems are integrated into one another, a blend door controls the mix of cold and hot air into the cabin to provide you with your desired temperature.
• Evaporator: An evaporator is typically part of a vehicle’s air-conditioning system. However, it may be integrated into the heating system. It dehumidifies the air before it flows into the cabin.
• Thermostat: Any component that monitors heat.

One quick check

For the coolant to receive heat from the engine, the engine must be running. If you’re only noticing cool air when you first turn on your vehicle, make sure you’ve driven for at least five minutes before looking into why the air is blowing cold. By then, warm air should be coming through the vents.

If you don’t feel the heat, continue reading to learn more about why your car is not blowing hot air.

What can go wrong with your vehicle’s heating system

Because a vehicle’s heating system is complex, any number of issues can crop up. We’ll cover the most common ones here.

Contaminated or low coolant

Ensuring appropriate levels of clean coolant should be a part of your routine maintenance schedule. When your coolant is contaminated, or levels have dropped, your heating system will have difficulties moving heat into the cabin. Having your coolant checked and replaced is an easy fix to this problem.

Problems with the thermostat

If the thermostat can’t measure temperature, your vehicle can’t produce the temperature needed for your comfort. A broken thermostat can also make your cabin feel like you’ve turned on the air conditioner.

Problems with the heater core

The heater core comprises several parts, any of which can break down. Although you may feel some heat from your vents if the heater core is broken, that is only the residual heat that has travelled through the heater system from the engine. It won’t be much, if there’s any at all.

Blower fan broken

If any of your blower fans are broken, you may notice weaker air flow as well as cold air.

Blend door stuck in cold position

If the blend door remains in the cold position, it won’t be able to mix hot and cold air to produce the temperature you selected for the cabin.

Heater hoses damaged

A lot of hoses run through your vehicle, such as radiator hoses, brake hoses, power steering hoses, and more. Heater hoses, like all the others, can be damaged or leaking, which will affect the flow of coolant to and from the engine.

Enjoying the heat again

An experienced mechanic can find out why you’re not getting hot air in the passenger cabin. Once they’ve diagnosed the problem and informed you of it, they will repair it. Contact your nearest NAPA AUTOPRO service centre to book an inspection with one of our experts.

For more tips on getting your car heater ready for winter, check out this article.

Picture courtesy: iStock-1302070179