Cold Cars: Common Car Heater Problems

During the winter, you rely on your car’s heater to keep you warm on your drive and improve visibility. So when your car’s heater breaks, you face danger as well as discomfort. After all, you can’t defog your windshield if your defogger won’t work.

Before you haul your car into the repair shop, take a look at some of the most common causes for car heater breakdowns. You can get an idea of what your problem might be, how you or a mechanic can fix it, and roughly how much you’ll have to pay to get your heater back in good working order.

Low Coolant Levels

Your car’s heater works by using warmth from the engine to heat the vehicle’s interior. As your car runs, it naturally heats up its coolant, which is usually a mixture of antifreeze and water. The hot coolant then runs through tubes over to the heater core and a fan blows the hot air out through your car’s vents.

When your car has a coolant leak, it won’t provide the heater core with enough hot fluid to generate warm air. A coolant leak also puts your engine at risk for overheating and can seriously damage your vehicle.

Coolant most often leaks out through worn seals on water pumps, corroded radiators, or cracked hoses. Your mechanic might also find leaks through the freeze plugs, heater core, or gaskets. Even if you can’t fix the leak yourself, you can figure out you have one by checking your reservoir levels, and watching for spots or puddles under your car after its been parked for a while.

How much a coolant leak costs to fix depends on the leak’s location. If it’s a broken hose, it will be relatively inexpensive. However, a leak through the heater core could take a long time to fix and cost several hundred dollars.

Bad Thermostat

Your car’s thermostat determines when to let coolant flow through the engine. If your engine is cold, the thermostat stays closed until it warms up and reaches an adequate operating temperature. Once your engine heats up, the thermostat opens and lets coolant circulate.

Broken thermostats don’t register when engines need coolant. Since your heating system relies on hot coolant from the engine, a broken thermostat will mean only cold air comes through your vents. A broken thermostat can also cause your engine to overheat, so it’s important to get it fixed.

To repair your thermostat, the mechanic will have to take out a radiator hose, remove the broken thermostat and install a new one. This process shouldn’t take long, but can cost a couple hundred dollars.

Broken Blower Fan

The blower fan in your car’s heating system takes the hot air from the core and distributes it through your air vents. Even if every other component in your system works, you won’t get any hot air with a broken fan.You can easily diagnose a broken blower fan yourself. If your fan isn’t working, you won’t feel any air, hot or cold, coming through your vents. The fan might have a motor problem, a short circuit, or a faulty switch. A mechanic will be able to thoroughly diagnose the issue and repair or replace the broken connection.

The fan itself can be a pricey part to purchase, so plan on spending a few hundred dollars on this repair.

Contaminated Coolant

Even when your car has adequate coolant levels, the heater core can’t use the coolant properly if it’s contaminated. This usually means your coolant contains too many rust particles or bits of some other substance. These contaminants cause blockages so your heater core can’t circulate coolant and distribute warm air.

To fix this problem, either you or a mechanic will need to flush out the system and replace the coolant. If you leave the fluid contaminated, you won’t just have to live with a broken heater—you might also face a damaged radiator or a faulty gasket.

A system flush costs less than many other heater repairs and requires less work.

Corroded Heater Core

The heater core in your car works like a radiator to move hot air through your car’s vents. Damage to your heater core will have some telltale signs. Excessive condensation on the inside of your windows tends to indicate a leak. Your heater will also only give off lukewarm or cold air if your core has a problem.

The heater core sits behind your dashboard on the passenger side. It’s difficult to access because it’s buried under many other car parts. Since it requires so much work to get to and replace, heater cores cost repairs come with high costs. Plan on spending anywhere from $500 to $900 on this repair.

When your heater breaks down, you need to quickly figure out the issue and get it repaired. Use these common problems as guidelines to diagnose your heater’s issue and get your defroster back in business.