Four common causes for a vehicle heater not working and their related parts.

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Is The Heater in Your Car Not Working?

The heater isn't working because of issues with the blower motor. This can be caused by internal damage or wiring problems preventing power from getting to the blower motor. However, in less common cases, the issue might be related to something different, like a restricted heater core, faulty blend door actuator, faulty coolant control valve, faulty heater fan, or a stuck-open thermostat.

Consider consulting a skilled expert who can pinpoint and recommend future actions to prevent and fix the broken car heater. This keeps your vehicle running smoothly, allowing you to enjoy a cozy ride worry-free. Remember, if left unattended, a minor glitch can snowball into a major headache.

Watch out: A car heater not blowing hot air can involve several different car systems! Ignoring heating problems can jeopardize your comfort, create further issues, and drain your wallet.

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The most common causes for the car’s windshield wipers not working:

Faulty Blend Door Actuator: A blend door actuator is a small motor that controls the position of the blend door in the vehicle's HVAC(heating, ventilation, and air conditioning) system. The blend door is inside the dashboard and it smartly mixes the heater air with AC air to get the exact temperature you set on the dashboard. However, if it fails, it'll mix wrongly and cause different temperatures.
Faulty Blower Motor Wiring/Connectors: The blower motor is an electrical device that blows the air from inside the AC system to outside, so it can travel through the vents and get inside the cabin. However, if the blower motor is faulty due to bad connectors or wirings, it won't blow, resulting in bad airflow and a malfunctioning heater.
Broken Blend Door: The blend door itself is a plastic barrier that moves in command of the blend door actuator. It separates the heater air from the AC air, and it decides when to mix them to regulate temperature according to what the driver wants. However, if the blend door is damaged, cracked, or misplaced, it won't separate the AC and heater air, resulting in wrong temperatures and malfunctions.
Thermostat Unable to Close: The thermostat is a device that opens up by itself, pinging the radiator to send coolant to the engine, avoiding overheating. However, if the thermostat fails and gets stuck open, coolant will be constant, and the engine might become too cold. Since the heater uses hot vapors from the engine, it'll stop blowing hot air.
Restricted Heater Core: The heater core looks similar to a radiator, but it's much smaller and it sits behind the dashboard, inside the AC system. The heater core gets hot coolant from the engine and uses it to warm the air inside the heater. If the heater core fails, the heater won't blow warm air.
Faulty Coolant Control Valve: The coolant control valve decides where to send coolant throughout your vehicle, controlling how much the engine and HVAC get of it; it's a gatekeeper, halting and sending coolant according to the vehicle's needs. However, if the coolant control valve fails, coolant flow gets disorganized, which can result in heater problems.

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Frequently Asked Questions

Is the heater blowing ambient-temperature air?

The heater core has a passage where a liquid called engine coolant flows through it. A blower motor pushes air across the heater core's fins to heat the air. This air absorbs heat from the coolant, warming it before entering your car's interior. However, if the heater core gets clogged over time due to a lack of maintenance, it restricts the coolant flow. This reduced flow means less heat is transferred to the air, and that's why you might get lukewarm air from the heater. In rare cases, the heater might also blow cold air, emit a sweet smell, or clicking noises.
Does a clicking noise come from the dashboard when adjusting the heater's temperature?

Inside your car's dashboard, there's a "blend door" that controls the heater's temperature. It makes the air colder or hotter, depending on what command it gets. This door moves because of a little motor called the "blend door actuator," but its gears can wear out over time, causing problems. You might notice temperature issues and hear clicking noises when adjusting the temperature. In rare cases, the "check engine" light also lights up on the dashboard, and the heater blows weak air.
Is the blower motor unresponsive or working intermittently?

The blower motor in your car's heater is like a fan that pushes air across. Over time, this motor can wear out and draw more electrical current. When this happens, the wires and connectors can get hot and melt, leading to a weak and intermittent connection. As a result, the blower motor may work sometimes but not always. More rarely, this can trigger the "check engine" light on the dashboard.
Is the heater blowing cold air even after warming up the engine?

Certain vehicles have a valve called the "heater hose control valve." Its job is to restrict the amount of hot coolant that goes into the heater core, which helps improve the effectiveness of the air conditioning system. This valve can operate in different ways: mechanically, by vacuum, or electronically. If this control valve malfunctions, it restricts the hot coolant flow to the heater core. As a result, even after the engine warms up, you won't get any hot air from the heater vents. In rare cases, this might accompany a coolant leak, weak airflow from the vents, and clicking noise under the dashboard.
Is the temperature coming from the heater always the same regardless of your adjustments?

Inside your car's heating and air conditioning system, there's the "airbox." It has plastic doors that control the airflow to manage the temperature. These doors are moved by small motors called "door actuators." If these doors break, the actuator can't control them anymore and gets stuck in one position. Since the doors blend hot and cold air, the temperature won't change, no matter what you set on the control panel. This rarely accompanies a "check engine" light on the dashboard.
Is the "check engine" light active on the dashboard?

The thermostat in your car helps the engine warm up in a calculated time to reduce emissions. But it can get stuck open and break down after wear and tear. When the thermostat sticks open, the engine takes longer to reach its ideal temperature. This warm-up delay is alarming to the engine computer, activating the "check engine" light on the dashboard.

Typical fixes to address the cause(s)

These are typical processes and repair services that fix a check engine light issue

The most common cause: Faulty blower motor wiring/connectors

The most common reason for a car’s heater to stop working is due to a faulty blower motor. The blower motor can stop working due to connectivity and wiring issues. Your vehicle's heating system needs the blower motor to blow warm air through the AC vents. However, if the blower motor doesn't work, your vehicle's air vents won't blow any air.

Symptoms it causes: Apart from the heater not working you might notice AC issues, humming noises, a burning plastic smell, etc.
Medium risk of priority: Wiring problems with the blower motor can result in warm air accumulating inside the system, and overheating other components. Additionally, a faulty blower motor might overstress other components like the blend door, leading to heftier repairs.

How exactly does the blower motor wiring fail?

The blower motor relies on wirings and connectors since it needs power to work. However, electrical problems can pop up leading to short-circuit and overstress, resulting in wiring issues. Additionally, driving conditions can also strain the blower motor wiring due to friction and vibration from rough driving.

Go safe: Ask for a mechanic to inspect your vehicle’s HVAC system to investigate if the blower motor is faulty due to surrounding components and if there’s further damage to check out. Many shops do transparent vehicle inspections and lay out your options after investigating your vehicle’s conditions.

What’s a vehicle inspection? It’s “detective work” on your vehicle, checking its systems to see if anything prevents the car from working as expected. In this case, mechanics examine different parts of your vehicle to track if anything is causing the blower motor wiring to wear out. They’ll also check the condition of components during their inspection, noting which are causing the problem and which got affected by it, recommending to replace them in order of priority.

Transparency example in a faulty wiper motor service

An HVAC system inspection is the most transparent process to understand why your vehicle’s air filter is faulty. This is because many components surrounding the air filter, blower motor, and blend door can have a say in the issue, indicating the real culprits that caused it all.

Let’s read an example of how this kind of inspection helps to service a faulty blower motor wiring.

A customer brought their vehicle to the shop because its heater wasn't working properly. Sometimes, it worked fine in all settings, but in others, only at high-speed settings. They noticed that if they set the blower at high speed, it would work, and then they could adjust it to slower speeds. However, it never seemed to work if they tried starting it at a low-speed setting.

During the test drive, the technician observed that the blower motor worked inconsistently. While doing a vehicle health inspection, the technician found nothing relevant.

After the customer approved additional diagnostics, the technician accessed the blower motor and blower motor resistor under the dashboard. When attempting to back probe the electrical connector to the blower motor, they discovered the connector was melted.

Nevertheless, the technician tested the voltage to the blower motor by back-probing the connector anyway; they found that the voltage was present at all speeds. This evidence indicated that the blower motor and its pigtail were melted causing the heater to work only sometimes at specific wiring angles, and would need to be replaced.

A blower motor with wiring issues can melt connectors and malfunction