Why is my car heater not working? Possible causes, and what you can do

Not only is it uncomfortable, but it could also even be dangerous.

Getting your car serviced regularly is the best way to prevent heater problems. If you find it hard to make time to take your car to the garage, try RAC Mobile Mechanics. We come to you, servicing your car in your driveway at home or work. But if, despite your best efforts, you get caught out by a car heater that’s not working, here’s what it could be – and what you can do.  

Car heater not working at all – what could it be? 

If there’s no heat or airflow when you turn on your car heater (so, your car heater isn’t working at all) it’s likely to be one of these issues:

• A problem that’s stopping power from reaching your blower motor, like an electrical problem or a blown fuse.  
• A faulty blower motor that’s preventing air from coming through the vents. There are a few reasons your motor blower could be failing, such as age, damage, a faulty resistor, or a blown fuse. 
• The heating system switch may be faulty.
• The heater core may be blocked.
• The cabin air filter may be damaged or clogged.

If you’re troubleshooting car heater failure, you should check your car’s fuse box and rule out any blown fuses. The owner’s manual will tell you which fuse controls the heating system, and you can usually find the fuse box under the dashboard or bonnet.

It’s not a good idea to examine your own blower motor, though, or replace blown fuses yourself if you don’t have the required mechanic knowledge to carry out the work.  That’s why we recommend consulting a trusted mechanic, or use an RAC Approved Garage.

Why is my car heating blowing cold air? 

It usually takes a few minutes for a car’s heater to warm up, but if you’ve waited and your vehicle’s heater is blowing cold air, it could be one of several issues.  

Car heaters use hot coolant to create warmth, so low coolant levels are common causes of car heater problems. Check your coolant levels are topped up, and that your coolant to water ratio is correct. Just make sure your engine is cool while you’re topping it up and ensure the vehicle is parked on a flat surface.

Faulty thermostats are another common cause of car heaters blowing cold air. If yours is jammed in the open position, your car will get too cool. This means the coolant won’t get hot enough to create hot air. If this is the case, your thermostat may need replacing.  

Other common problems include clogged or damaged heater cores, system malfunctions, water pump failure and problems with the blend door.

It’s best to get your car checked by an experienced mechanic – incorrectly diagnosing the reasons why your car heating isn’t working could make the problem worse.   

Troubleshooting car heaters: some simple steps 

Troubleshooting car heater issues yourself could give you a better idea of how much repairing your car heater might cost. These are a few simple steps you can take to troubleshoot car heater problems:

• Check the coolant level – low coolant can result in your car heating blowing cold air. Look for leaks, or puddles of coolant under your vehicle.  
• Inspect the dashboard thermostat to check it’s not stuck open. If it stays low, you might need to replace your thermostat. 
• Check your car’s heater core by holding your hand to the airflow – if it’s weak, the heater core could be clogged.  
• Listen for clicking or grinding noises that might mean a problem with the blend door, or whining noises in the water pump which could signal a fault.

If these steps don’t help, have a look under the bonnet. If you see fluid leaks, damaged hoses or loose connections, these might be the reason your car heater’s not working. If everything’s working normally, you might have a problem with the cabin air filter.  

If troubleshooting car heater issues on your own doesn’t help resolve the issue, it’s time to consult a mechanic.  

How much to repair a car heater?

If you’re worrying how much car heater repairs could cost, you’re not alone. Car heater repair costs can vary quite a lot depending on the underlying issue, but the labour involved can make repairs expensive. If you’re lucky, your car will only need a cheap fix like a coolant top up or a replacement fuse. If you’re less lucky, you could be looking at costs into the hundreds or even thousands.  

Pricier problems include anything involving your car heater matrix, as these tend to be located deep in the dash or footwell area of your car. It can take a lot of time to take everything out and refit it. Issues with your blower motor might be a bit cheaper. But how much it costs to repair a car heater can vary quite a bit depending on location. Who you pick to do the work makes a big difference too – an honest, trustworthy mechanic will charge less than someone looking to make a bit extra by ramping up the cost.  

RAC Mobile Mechanics are honest, expert, and come right to your home or place of work. There are no hidden costs – all quotes include parts, labour, and VAT. Give us a call if you find your car heater not working, and we’ll help you get your car warm and fit for winter travel in no time.