My car won’t get warm!

We’ve had a pleasantly warm December. What’s in store for temperatures the rest of this winter is anyone’s guess.

Some people will come to the point that they can’t get hot air from their heater or defroster. If this happens to you, the first task is to check your anti-freeze, or coolant, level. The most common cause of a lack of heat is low coolant level. Most cars have a translucent plastic reservoir under the hood, typically towards the front, to the left or right side of the radiator.

It is important to check the coolant level immediately. If it is low your car could also overheat. The first stage of low coolant level is a lack of heat. The next stage is that your car overheats. It is bad enough having no heat when it is 20 degrees outside. It is something worse to have your car overheat – leaving you stranded on the side of the road – when it is cold and dark outside.

If you find your coolant low you should add some. Ideally you want to add a 50/50 mix of antifreeze and water. It is becoming very common for stores to sell antifreeze pre-mixed to this ratio. There are also several types of antifreeze, however, you can buy a universal antifreeze that is compatible with all types. It would be most convenient to buy pre-mixed, universal antifreeze.

If you are going to immediately drive to a repair center, you could add straight water. Adding straight water allows the coolant to freeze at warmer temperatures, so don’t wait several nights before having your car looked at. If you don’t have any anti-freeze on hand, it is better to add straight water than to continue to drive with a low coolant level.

If your car is low on coolant, there is most likely a leak. You probably haven’t seen a puddle of coolant on the ground, but while driving you have a slow leak that gets blown away by windage when driving. Antifreeze doesn’t evaporate. If you are low on coolant, you should have your car checked.

If the coolant level is correct and you do not have heat, you may have a bad thermostat. The thermostat is a very simple metal spring device that opens and closes based on coolant temperature. It has no external controls. If the thermostat sticks open, you will be able to get hot air when it is warmer outside, but not when it is cold outside. The radiator is cooling the coolant too much. The thermostat should have closed to keep the engine and heater hot, but it is not operating properly. On some cars the engine temperature gauge will register lower than usual. Many cars have a computer controlled gauge, and the computer won’t show you that the coolant is colder than usual.

Another possibility is that the heater core is plugged or fouled. Failure to regularly flush the cooling system allows contaminants and sediment to build up in the heater core. Sometimes it is possible to disconnect the heater hoses and carefully flush the sediment out of the heater core with fresh water. Other times there is not a sediment blockage, but rather a residue coating inside of the heater core. The residue acts as insulation and the heater core won’t produce hot air. In this case it is usually necessary to replace the heater core.

Brian Klaubert has written for the Neighborhood News for four years, and owns Christian Brothers Automotive – Hamilton Mill on Braselton Hwy in Dacula. They have been voted Best of Gwinnett in both the Gwinnett Daily Post and Gwinnett Magazine.