The first truly cold morning of the season is when a lot of people find out their heater isn’t working. You crank it all the way up, wait a few minutes, and the vents are still blowing cool air. Nobody wants to start a Tennessee winter like that.

It helps to know how your heater works. Your car doesn’t have a separate furnace. It borrows heat from the engine by running hot coolant through a small radiator behind the dashboard, called the heater core. A fan blows air across it and into the cabin. So when the heater stops working, the cause is usually somewhere in the engine’s cooling system.

One of the most common reasons is simply low coolant. If there isn’t enough fluid in the system, not enough of it reaches the heater core. Low coolant also means there’s a leak somewhere, and that’s worth finding before it causes the engine to overheat.

Another frequent cause is a thermostat that’s stuck open. The thermostat is supposed to stay closed until the engine warms up. When it sticks open, the engine never reaches normal temperature, so there’s never much heat to share. A good clue is a temperature gauge that stays lower than usual even after you’ve been driving a while.

There are a few other possibilities too, like air trapped in the cooling system, a clogged heater core or a small door inside the dash that controls hot and cold air and has stopped moving.

Pay attention to a couple of warning signs. A sweet, syrupy smell inside the car, or a greasy film that fogs up the inside of the windshield, can point to a leaking heater core. A puddle of green, orange or pink fluid under the front of the car means coolant is escaping. If your temperature gauge ever climbs toward hot, pull over safely and turn the engine off, because driving an overheating engine can lead to very expensive damage.

At Exhaust Plus Auto Center, our heating and A/C service starts with finding the real cause, so you aren’t paying to replace parts that weren’t the problem. Whether it turns out to be a simple coolant leak or a thermostat, we’ll explain it plainly and get the warm air flowing again.

Call us at (931) 388-8411 or stop by 102 W 5th St in Columbia, Monday through Friday from 8 to 5.