Heater Blows Cold Air? February 14, 2016 Jeremy Turner 0 Comments Heater Blows Cold Air? A heater that blows luke warm or cold air can be the symptom of several possible issues. It could be as simple as low coolant or it might be something more serious. But there are a few tests you can do to clue into the issue. The heater is a pretty simple system. Coolant is run through the heater core in the dash. When the car is warm the coolant will warm up the heater core and air passing over it will heat up. Low Coolant One of the most common causes of a heater not working is low antifreeze. You can check it by taking the radiator cap off WHEN THE CAR IS COLD. If the coolant is at the top then the level is fine. If you can’t see the coolant you can top it off with antifreeze or in a pinch you can use water. Clogged Heater Core Another possibility is that your heater core may be clogged. If the coolant level is okay, you can touch the heater hoses to determine if the heater core is clogged. The heater hoses are rubber hoses that are usually about one inch in diameter. They will be going from the engine to the firewall, the metal partition between the cab and the engine, usually on the passenger side. When the engine is warm you can touch both hoses. If one hose is significantly warmer than the other, then you probably have a clogged heater core. Blend Door Issue The blend door is the door in the dash that switches between hot and cold. To check if there is an issue with it turn the car on and switch between hot and cold. If you feel any difference in the temperature then the blend door is moving at least a little. If there is no change in the temperature then you might have a broken blend door or the motor that moves the door may be broken. Remember that these tests aren’t definitive but they will point you in the right direction. CategoryBad Heater, Blend Door, Evaluations, Heater Core, Low Coolant, Repair, Services Like Tweet +1 Pin it Write a comment: You must be logged in to post a comment.