With autumn right around the corner, you can expect to experience chilly nights again soon, meaning that you'll want your furnace to be in top shape. After all, fewer things are more unpleasant than being woken up at night by freezing indoor temperatures because the furnace has broken down. You can circumvent this problem by being aware of signs that your furnace may be on the verge of malfunctioning and contacting a heating service professional to inspect and repair the system before it breaks downs. Following are three signs that indicate that your furnace needs a checkup. 

A Yellow Flame  

If your furnace flame is yellow rather than blue, that's a strong indication that your furnace is malfunctioning. The flame should be clear and blue -- a yellow flame means that the carbon monoxide is being produced, which can be deadly to household residents and pets. Have your furnace checked out immediately if the flame starts to burn yellow instead of blue. 

Blowing Cold Air

If your furnace sometimes blows cold air, that's often a sign that something is wrong with its internal mechanism, such as bad valves or clogged pumps or other components. However, the problem could be as simple as a lack of fuel, so be sure to check your fuel source before calling in a technician. Another reason your furnace may be blowing cold air is because your air filter is clogged. This may cause the furnace burners to automatically shut down as a way of keeping them from overheating, but it won't stop the fans from blowing cold air. Ductwork that has been damaged or has come unhooked may also result in cold air leaking into the system. 

Strange Noises 

Furnaces frequently make strange noises. Some aren't indicative of a serious problem -- for instance, popping and pinging sounds are usually coming from the ductwork and are no cause for alarm. Metallic chirping sounds may be a result of a blower wheel that has gone out of its alignment, which is a minor problem that most people can fix themselves. However, vibrating and whining noises usually indicate serious problems, and loud thuds and booms can have a variety of causes, including duct issues, dirty burners, and defective gas valves. 

For more information on keeping your furnace running like a top through the cold fall and winter nights ahead, contact your local HVAC contractor today for heating service to ensure that you and other household residents don't wake up to a freezing house.