What Could Be Causing Your Furnace to Give Out Cold Air

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The main purpose of the furnace is to generate heat and provide warmth. But your furnace isn’t sending out any heat. Instead it’s doing the opposite. Furnace problems on the horizon? Time to take a closer look 

Here’s what could be causing the furnace to blow cold air.

Takes Time
If your furnace is slow only in the initial stages and and there is no heat from furnace only at the beginning, then probably there are no major furnace problems to solve. When you switch on the hot water tap, it takes a little time for the water to turn warm. Similarly, it takes some time for the warm air to start blowing through your heating registers.

Furnace Overheated
Your furnace starts blowing hot air, then cold air and then stops blowing any kind of air completely. When this happens, you should check if your furnace is overheated. If so, the limit switch, a furnace safety device, turns the furnace burners off. The blower keeps blowing to cool the furnace down to a safe level. What mainly causes overheating furnace problems is a dirty furnace air filter. The dirty air filter will block the air-flow, causing the furnace to run longer so that it ends up overheating. Always best to change filters in such cases.

Flame Sensor
If you’re getting warm air when your furnace comes on, and then it quickly goes cold, this could be the problem. If the flame sensor is dirty, it is not possible for the gas burner to stay lit. For such furnace problems, you will have to call professionals or fix the burner yourself.

Thermostat is ON
Another reason for the furnace to blow cold air is that the setting on the thermostat is ON. Is the furnace’s blower constantly running? Check your thermostat. That’s where a technician will start first, hence you should as well. If your thermostat’s fan setting is set to ON, the furnace blower will keep running even when your furnace isn’t heating the air. You can turn your thermostat’s fan setting to AUTO to solve this small issue. Now your furnace will be able to blow warm air.

Pilot Light
If your furnace is blowing only cold air, it is possible that your pilot light may be out. Relight the pilot light if it isn’t on. In order to do this, you will have to follow the manufacturer’s instructions exactly as given. You can usually find them attached to the furnace. Make sure the furnace’s gas valve switch is in the "on" position ( i.e parallel/in line with the gas supply pipe.) If the switch is on, then check to see if the pilot light is dirty. If it is, clean it to allow gas to come through. Ensure that gas is flowing through the furnace. At times there could be a problem with a thermocouple (the copper rod you see the pilot flame hitting). If the pilot lights and doesn’t stay lit, then it needs to be adjusted or replaced.

Again if you don’t know how to go about changing things that need to be, please contact a professional if even after checking all the above things, there is still no heat from furnace. Furnace problems are usually easy to tackle.