When a car’s heater is not working in the middle of winter, it can make your daily commute miserable and cold. On top of that, if there’s no heat in the vehicle, it has no way to defrost the windows and mirrors to eliminate condensation and ice. Having no working heater can be a potential safety hazard and you definitely don’t want to end up stranded in inclement weather. So, why isn’t your car’s heater working and what can you do to fix it?

Cooling system

A vehicle’s cooling system works like a small radiator. Once the engine achieves the right temperature, with help from the thermostat, it heats the coolant and water mix. That mixture passes to the heating core using hoses and valves. The fan blows the heat away from the core and distributes it into the cabin of the car.

If the coolant level is low, the core isn’t working, or there’s air in the system, your car’s heater may not work.

The coolant itself could also be an issue. If there are rust particles or other contaminants in the coolant, it could prevent the heating core from distributing heated air into the cabin.

Ensure your heater’s coolant level is where it’s supposed to be and that the coolant isn’t contaminated. If you have a low coolant level, make sure you don’t have any leaks in the system. Coolant doesn’t evaporate on its own.

Fan

If the coolant is where it should be, take a look at the fan. The heater may be doing its job. But if the fan stopped working, that’s why heated air isn’t reaching the cabin of the car. If you don’t hear the fan running, it may be your culprit.

First, be sure to check the fuse and make sure it isn’t blown. If it’s not a fuse issue, you may need to replace the fan, which you’ll find inside your vehicle’s dashboard. This is more common with older cars.

Thermostat

A faulty thermostat could be behind your car’s heater not working. If it isn’t opening up to let the coolant flow through it, the core can’t produce heat.

Thermostats can also get stuck open causing the engine’s temperature to stay low.  If the thermostat is the culprit, you may have bigger problems because the vehicle will start to overheat. And that’s a bigger problem than not having a heater.

Preventive maintenance

Simple maintenance can help you prevent future problems with your car’s heater. 

• Ensure that you have a full coolant level at all times because it helps the unit’s core to heat up. It also helps to keep your vehicle’s engine running smoothly.
• Make sure that the coolant in your vehicle’s system is clean and free of any rust or other debris. The coolant in a newer vehicle may not need service until the vehicle reaches 60,000 miles. 
• Check that the thermostat is working as it should. You can remove it from the engine for testing. With a pair of pliers to hold it securely, place it in water and see if it opens as it should at a given temperature. If it seems to be in good working order, take a look at the fan.
• Make sure you can hear the fan running. If you can’t hear it, first check the fuse to make sure it hasn’t blown. If the fuse is okay, it may be time to replace the unit’s fan.
• Check all belts and hoses to make sure they are properly attached and not leaking.

The heater in your vehicle isn’t like a furnace that you’d find in a house. When a furnace malfunctions, you replace the entire unit. With the heating system in a vehicle, there are many problems that can arise. The system has several different components that work together to provide heat.

When something goes wrong with the heating system in your car, the type of repair needed depends on what the exact problem is. If it’s a repair you can’t make, or you can’t figure out what the problem is, have a mechanic assess your car’s heating system.