Why Isn’t My Car Heater Working? This List Brings the Heat


First thing in the morning, there is only one thing worse than getting into a cold car and trying to get the kids to school or make it to work: that’s having a car heater that doesn’t work. At best, a car heater that isn’t working is a real headache – and in some situations it can be downright dangerous. Unfortunately, there are a number of common reasons why your car heater may not be working. But, we are here to help you find out what the problem could be so you can get it fixed or get that upgrade you’ve been needing. These are the 7 common reasons your car heater isn’t working.

Car Heater Thermostat is Faulty

Across almost all models of cars and trucks, the number one cause for a vehicle’s heater to stop working is a faulty or broken thermostat. The thermostat in your car gauges its temperature and helps to regulate engine operation based on feedback – in more modern vehicles in the thermostat also helps the engine computer to set the right fuel-to-air mixture in real time. A damaged component or malfunction can get a thermostat stuck open or closed. That can cause issues with your heater working but also damage your engine’s cooling system. A broken thermostat makes you uncomfortable during a trip – but it can also overheat and ruin an engine.

Car Heater Has Low Antifreeze/Coolant

The second-most common issue is low antifreeze or coolant. Leaks mean low fluid, and when a vehicle’s coolant/antifreeze levels drop, there is simply not enough fluid to do the job. The hot fluid can’t make it to the heater core and though everything is working properly, your interior never heats up. Leaks aren’t the only culprit, though. Low fluid can be an issue if your engine overheating and burning off fluid, or if it wasn’t properly filled to begin with.


Faulty Heater Fan

This one is almost more frustrating because of its simplicity. Sometimes all the coolant, mechanics and other parts might be working well – but the heater fan might be out of order. The heater fan isn’t special; it just blows the heated hair into the cabin. But when it breaks or suffers an electrical short, the warmed air never gets where it needs to be to keep you cozy!


Car Heater Blower Motor Resistor is Faulty

Blower motor resistors are small electrical components that regulate the amount of power going to the blower motor. Some vehicles are notorious for wearing them out sooner than expected. If the blower motor resistor is broken, you will probably be unable to set the fan speed, or it may shut down and you won’t be getting warm air flow at all.


Leaky Radiator

A leaky radiator can lead to a damaged engine, but at the very least it will prevent coolant from getting to a car’s heater core – meaning you stay cold. Radiators, hoses, and hose connections gather dust/dirt and rust that can corrode the radiator, the most common cause for leaks. Sloppy service can also cause leaks: over-filling the radiator can increase water pressure and spring a leak. Other parts, like a faulty thermostat or a heater core may also cause a leak by providing too much heat and pressure.


Faulty HVAC Controls

Each year, more vehicles use more electric components. That adds convenience but also opportunities for a short or malfunction. The buttons, knobs, or even touchscreens might be failing and preventing your car heater form working properly.


Faulty Wiring or Blown Fuses

When you turn on the controls and the heating system doesn’t respond, it might have nothing to do with the heating system at all – it might not even be getting the message! Time and corrosion can break down electrical systems, your car’s wiring might be broken or have a short in it. That means when you are turning the dials or hitting the buttons, nothing is triggered – and you’re left shivering.


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