To avoid turning into an icicle and save your engine from potential catastrophe, let’s explore the causes, diagnosis, and other related aspects involved.
This Article Contains:
- 7 Causes of a Car Heater Blowing Cold Air (+Solutions)
- How to Diagnose a Broken Car Heater?
- How Much Does a Car Heater Repair Cost?
- 4 Car Heater FAQs
Let’s get your car’s heater blowing warm air again.
7 Causes of a Car Heater Blowing Cold Air (+Solutions)
Here’s why your car heater could be blowing cold air:
1. Low Coolant Level
Typical heating systems use coolant (glycol and water) to absorb engine heat and warm the cabin. But over time, vehicles can run low on engine coolant.
Low coolant means less heat absorption, causing cold air to blow from your heater.
2. Coolant Leaks
A coolant leak will result in (yes, you guessed it) low coolant levels — leading to a malfunctioning heater system, and your cabin won’t receive hot air.
Be sure to check the radiator, radiator cap, hoses, and water pump for leaks since they’re susceptible to wear and tear.
3. Broken Thermostat
The thermostat opens to release coolant when the engine reaches an operating temperature threshold. However, a broken thermostat may not open correctly.
A faulty thermostat results in insufficient heat absorption, which poses the danger of the engine overheating. Additionally, your car heater will blow cold air.
4. Air in the Cooling System
Air bubbles in the cooling system disrupt the coolant flow, which hinders sufficient heated coolant from reaching the heater core. Insufficient engine coolant flow means the heater core can’t properly heat the air passing through it.
5. Clogged Heater Core
The heater core uses hot coolant from the engine to heat the air passing over it. The heater fan then pushes the warm air into the cabin.
Unfortunately, the heater core’s tubing can get clogged with debris. When this heater core issue happens, the hot coolant can’t flow through the tubes to create warm air.
6. Jammed Blend Door
Your car’s heating system contains a flap called the “blend door,” which allows hot air from the heater core to enter the cabin.
When it’s blocked, cool air bypasses the heater core and enters the cabin unheated. This can happen due to debris build-up or problems with the blend door actuator (a device that opens and closes the door).
7. Broken Heating Controls
Two heating system control issues cause your heater to blow cold air:
- Broken or jammed heating control buttons
- Malfunctioning heater control valve
The heater control valve adjusts the amount of coolant flowing to the heater core. If it’s not working, there may not be enough coolant to heat the cool air that blows into the cabin.
Now that we’ve looked at the causes of a car heater blowing cold air, let’s get you defrosted with some diagnosis tips.
How to Diagnose a Broken Car Heater?
There are several ways to diagnose a car heater problem. Typically, a mechanic would:
- Inspect coolant levels and quality: They’ll access the coolant reservoir to see if the coolant level is below the guide mark or if it’s discolored (filled with debris). They’ll also also check for signs of a coolant leak.
- Check the engine temperature: Using an infrared thermometer, a mechanic will determine if the engine temperature is normal (190-220℉). If the operating temperature is outside this range, there’s likely a faulty thermostat.
- Inspect the heater core: The mechanic will open the heater box and look for signs of a plugged heater core. If the heater core is clogged, they’ll flush it with air or water.
- Evaluate the water pump: They’ll check all the cooling system parts, including the cooling fans, pump seals, radiator, and water pump pulley. They’ll also check the coolant flow through the system. Poor or no coolant flow may indicate a water pump issue.
- Assess the blower fan: If the air conditioning fan doesn’t engage properly when on the maximum setting, it’s likely an electrical issue. They’ll locate the problematic component using the multimeter.
- Flush the cooling system: If there aren’t any problematic components, a mechanic may flush any trapped air from the cooling system using a vacuum coolant filler.
- Inspect the blend door: If the blend door is blocked, clearing the debris would likely fix the issue. However, several components could be affected. A mechanic will assess what needs recalibrating, repairing, or replacing.
- Assess the heater control buttons and control valve: The mechanic would engage any controls and replace them if they’re broken or jammed.
While diagnosing the car heater problem, a mechanic will repair or replace the problematic heating system parts. Let’s look at the costs.
How Much Does a Car Heater Repair Cost?
Repair and replacement costs depend on the affected part of your car’s heater system as well as your vehicle’s make and model.
Here are some cost estimates (including labor):
- Coolant flush: $100 to $150
- Fan blower motor: $150 to $350
- Thermostat: $70 to $520
- Blend door: $150 to $550
- Heater control valve: $470 to $500
- Radiator: $200 to $1200
- Water pump: $680 to $810
- Heater core: $800 to $1000
Now that you know the costs, let’s satisfy your other curiosities.
4 Car Heater FAQs
Here are answers to some questions you might have about car heater issues:
1. Do Heater Problems Need Urgent Attention?
You should take your car to a mechanic immediately if your car heater isn’t working.
Certain issues like a coolant leak or cooling system blockage can cause engine overheating, which incurs high repair costs and may even put you in danger.
Other causes, like a faulty blower motor, won’t heavily impact your vehicle — you’ll just have air conditioner issues. However, if you’re driving in freezing temperatures, you need a working heater to stay safe too.
2. How Does a Car’s Heater Work?
Most cars have a liquid-cooling system, whereby a mixture of water and glycol (coolant) flows through the engine, absorbing heat. Some of this heated coolant moves to the heater core. When you turn on the heater, the air pushes over the heater core, eventually reaching the cabin.
3. How to Prevent Car Heater Problems?
Maintaining your car’s cooling system through regular servicing is the best way to prevent car heater issues. Your vehicle’s recommended routine maintenance schedule indicates how often a service is necessary. However, a good rule of thumb is servicing once a year.
4. What If There’s No Air Coming from the Heater?
The blower fan pushes hot and cold air into the cabin. If it’s not working, neither the heater nor the air conditioner will work.
There are many reasons for a failing blower fan, including a faulty motor, blown fuse, broken control resistor, or bad wiring. So, it’s best to have a mechanic diagnose the problem.
Several issues can cause a car heater to blow cold air, including a low coolant level, a broken thermostat, and a clogged heater core.
But don’t get frozen stiff.
RepairSmith will have your cabin feeling warm and cozy in no time!
We’re a mobile auto repair service that offers efficient online booking and is available seven days a week. We also provide a 12-month | 12,000-mile warranty on all repairs.
Contact us today for any car repair or maintenance service.