4 Reasons Car Heaters Fail

Making sure your vehicle produces sufficient heat is important not only for winter comfort, but for safe driving.

A broken heating system can be downright dangerous, should you be stranded in the cold. It can also render your defroster ineffective, creating a driving hazard.

Highly rated auto service providers tell our research team that, unlike a house, vehicles don’t have a central heater. Instead, a car’s heating system is essentially a combination of components.

The heat that warms you in the cabin originates with the engine’s coolant system. Once the engine reaches its operating temperature — controlled by the thermostat — it heats the mixture of coolant and water, passing it through hoses and valves and into the heater core, which resembles a miniature radiator.

A fan blows air over the heater core, pushing the warmed air through the cabin filter and into the cabin.

The fix for a heating problem will depend on its source. Auto experts tell us that these are common possible causes:

1. A cooling system leak that results in insufficient antifreeze and water in the radiator. A leak can be caused by something as simple as a loose hose clamp or it can be a sign of a more serious problem. Topping off the radiator fluid may help temporarily, but plan to have a coolant leak checked out. (Be aware that coolant in newer models may not require routine service until 60,000 to 100,000 miles.)

2. A faulty thermostat that doesn’t allow the engine to properly warm up.

3. A broken blower fan.

4. Coolant contaminated with rust particles or some other substance, creating a blockage that prevents the heating core from properly circulating air into the cabin.

Because several components comprise the heating system, it’s best to have a reputable auto mechanic diagnose and treat any problems.

Most heating-related repairs range in cost from $300 to $1,000, our research team learned, but an exact price can vary widely, because of the variety of issues that can create a heating problem.

To help ensure that your heating system performs when you need it most, have a mechanic regularly check the coolant level and other components, such as hoses and belts.