Is Your Car Heater Blowing Cold Air? Possible Causes

Reasons Your Heater is Blowing Cold Air in the Car

Identifying Heater Core Problems

Preventive Maintenance Steps for Car Heaters

Bottom Line

Your car heater blowing cold air can be caused by several problems, ranging from heater core issues to malfunctioning thermostats. With winter just around the corner, it’s more important than ever to start checking for heating and cooling system issues. This is one of the recommended ways to prepare your vehicle for the coming cold season.

Fortunately, car heaters blowing cold air is an easy problem to diagnose and troubleshoot, especially when you’re familiar with the common causes. In this article, we’ll talk about the possible causes of this problem and other related topics, such as identifying heater core issues and proper maintenance.

Reasons Your Heater is Blowing Cold Air in the Car

Similar to home heating, your vehicle’s heating system is made up of various components that work together to produce warm air. If one or two of these components fail, it’s enough to cause your car heater to stop working properly.

The following are some of the most common reasons your car heater blows cold air:

Heater Core Issues

Most heater-related problems are a result of a malfunctioning heater core. Your car’s heater core is a miniature version of a radiator. It’s often made of aluminum or brass tubing that helps the flow of hot coolant. The heater core is also responsible for your car’s defrosting and heating capabilities.

Heater core malfunctions can happen in two ways:

  1. The coolant cannot travel properly through the heater core.
  2. The air from the blower motor does not reach the coolant due to a clog.

The best way to confirm if the heater core is causing your car heating problems is by checking the coolant level. If the heater is blowing cold air but the coolant level is normal, it’s most likely a heater core problem.

Low Coolant Levels

Your car’s coolant cools down the engine regularly, especially during the hot summer days. If you turn up the heat during winter, your heating system brings the coolant over from the car’s engine to the heater core. Cooling fans will then blow the heat out into the car’s interior.

If there’s not enough coolant in the system, the heater core and cooling fans won’t be able to release warm air. That’s why the first thing you have to check when your car heater is not blowing hot air is the coolant level.

Turning on your heater would initially blow cold air because both the engine and the coolant need to warm up. This may take roughly 10 minutes. If the cabin remains relatively cold beyond that time frame, you may need to check the coolant level and have it replenished.

Broken Heater Controls

Over years of regular usage, the control buttons often jam up and simply stop working when pressed. This simple yet overlooked issue is sometimes the reason many car heaters blow cold air instead.

There’s also a heater control valve underneath your vehicle’s hood that acts as a switch to toggle the heat on or off. If that valve is no longer working properly, your car may be stuck with having cold air unless it’s fixed or replaced.

If your coolant level is normal, you can check the control buttons and the valve to see if they are still working as intended. Refer to the owner’s manual to locate them, since their positions often differ depending on the make and model of your car.

Malfunctioning Thermostat

One of the primary functions of your car’s thermostat is to tell the cooling system that the engine is starting to warm up. If the thermostat is not working properly, the cooling system won’t let the coolant cool the engine. That also means the coolant that will be flowing to the heater core doesn’t have enough heat to warm the interiors of your car.

A malfunctioning thermostat can easily be spotted by checking its gauge. Most modern cars, like the BMW, come with electronic thermostat gauges. If the gauge is stuck on the “C” even after the engine has been running for a while, that’s a sign of a malfunction.

Having your thermostat checked and replaced by a professional is considered the best and inexpensive way to resolve this specific issue.

woman checking her car

Identifying Heater Core Problems

Problems with your car’s heater core are often the reason your car heater is not working. However, they are often trickier to distinguish compared to other car heater issues because they also have their own set of symptoms that you need to watch out for.

The following are the telltale signs your car is experiencing heater core problems:

Very Sweet Smells in the Car

Have you started smelling something sickly-sweet in and around your vehicle? If yes, that could be a sign of a major heater core leak. This maple-like odor is probably radiator fluid leaking into your car.

The leaking fluid is usually blown out and fills the car’s cabin quickly. It’s also possible to smell this sweet odor from outside the car, especially if the radiator fluid or coolant has started spilling out onto the ground.

Problems with your car’s heater core are often the reason your car heater is not working

It’s recommended that you have your car inspected at the first sign of the sweet odor. Not only can the leak cause further issues with your car’s other components but prolonged exposure to the smell might cause health issues.

There’s Fog Inside the Car

One of the major symptoms of a damaged heater core is the heavy presence of fog inside the car. This type of fog isn’t just a simple mist found at the edge of your windshield. It covers every window with heavy condensation.

The fog usually shows up after a heater core blows up while driving. The leaking coolant starts evaporating and eventually turns into steam, which fogs up the inside of your car. Accompanying the fog is a strong and sweet odor that ultimately confirms it’s caused by a leaking coolant.

When your car starts fogging up while on the road, make sure to drive more carefully. Better yet, pull over to the side and have your vehicle towed to the nearest service center to be fixed. The fog might impair your sight when driving, so it’s best to have the issue addressed as soon as possible.

The Cabin is Colder than Usual

Another sign of your car’s heater not working properly is the quick and almost sudden drop in temperature inside the cabin. This happens when the car heater blows cold air in the car due to a leak or a blown-out heater core.

The drop in temperature is especially more pronounced during the winter months. You can also check if the cabin is getting colder than usual by feeling the passenger compartment. It’s almost always the first place that cools down when there’s a heating issue.

You can experience constant engine overheating and still be completely cold inside the cabin. That’s because there’s no longer enough coolant to cool down the engine and your heating system is just using air from outside.

Your coolant is one of your car’s essential fluids.

At the first sign of an increasingly cold cabin, it’s best to take your car to a specialist immediately, especially if you have started experiencing engine overheating. Ignoring this issue can cause further damage to your car’s other components.

car air conditioner

Preventive Maintenance Steps for Car Heaters

Just like any car component, the heating system is prone to breaking down due to regular wear and tear. However, there are simple preventive steps that you can do to help maintain their ability to function properly and extend their overall lifespan.

  • Maintain the coolant levels — Your coolant is one of your car’s essential fluids. It isn’t just for the air conditioning but it’s vital to your vehicle’s overall heating system as well. Make it a habit to check your vehicle’s coolant level every month and replenish them as needed.
  • Check for leaks — Coolant leaks are a symptom of car heater issues, so it’s only wise to always keep an eye out for them. Before you take your car for a drive, put in a few minutes to inspect the vehicle. Check for suspicious scents and signs of leaks underneath the car. If a leak is present, take your vehicle to a service center to have it addressed immediately.
  • Have annual inspections — Always schedule annual inspections for your vehicle to make sure they are working at peak performance. It can also help you identify underlying problems and fix them before they cause further damage. Some car care centers also offer winterization services where they check your vehicle’s heating system to make sure they are ready for the winter season.

Bottom Line

Having an effective and working heating system can make your winter drives a lot more enjoyable and safer. If you start noticing any issues with your car’s heating system, your best course of action is to have your vehicle checked and repaired as soon as possible.

Ignoring the problem may only lead to bigger and more expensive issues down the line.

Auto Works of Brandon provides quality auto care services for European and import vehicles like Audi and Mercedes Benz. If you start noticing car heating issues, don’t hesitate to schedule an appointment with us. Our team would be happy to help you get your vehicle repaired.


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