Furnace Blowing Cold Air? Even if you have a fairly new furnace, things can still wrong and cause this uncomfortable surprise. Sometimes you might be able to fix the problem on your own. However, it is important to know when the furnace repair professionals should be called so you don’t interrupt your business and spend time unnecessarily in the cold. Another thing you want to avoid is the risk of frozen pipes.
Related: Why is my furnace leaking water?
See Government of Canada recommendations on residential furnaces.
If your furnace is blowing cold air, try the following four furnace troubleshooting methods before you call a professional for assistance.
1. Check the fan setting on your thermostat (furnace blowing cold air)
Does your furnace sometimes blow hot air, but other times cold air? If so, the fan setting on your thermostat might be set to ON.
The blower is controlled by the fan setting, which is the part of the system that circulates air throughout your house. When the fan is set to ON this means your blower will run continuously – whether or not your furnace is heating air, which is why sometimes you end up with cold air.
Make sure the fan setting on your thermostat is set on AUTO instead of ON. When it is set to AUTO that will ensure the blower only runs when your furnace is heating the air.
2. Check your filter’s air filter (furnace blowing cold air)
If you have a dirty filter that can cause your furnace to blow cold air.
When an air filter is dirty it blocks the airflow across the furnace heat exchanger, which causes it to overheat. When your furnace overheats, it can end up tripping the high limit switch, which results in the furnace burners shutting off to prevent the heat exchanger from cracking.
Turn your furnace off at the thermostat and then check the furnace’s filter. Change the filter if it is dirty. You might need help from a technician to reset your furnace.
3. Check your furnace’s pilot light
If you own an older furnace that has a standing pilot light and it is not lit, the burners on the furnace will not light, which will result in no heat.
Use the following steps to attempt to relight the pilot light:
Step 1: Turn the furnace off. Switch the thermostat to OFF from HEAT.
Step 2: Locate the furnace’s reset switch and pilot light assembly. The switch and assembly should be close to the bottom of the furnace. If you are unable to find them, check the user’s manual for your furnace.
The cover on the furnace will need to be opened to gain access to the furnace’s reset switch. There should be a knob that has the following 3 settings on it:
Step 3: Turn the knob into the off position and then wait for 3 to 5 minutes. That will shut the gas down that comes through the pilot light.
Step 4: Turn the knob into the pilot position and then press down on the knob. That re-starts the flow of gas into the pilot light.
Step 5: While you are pressing on the knob, take a lighter and hold it over the opening of the pilot until it lights the flame. Once it is lit, the flame should look like a steady blue cone hitting the center of the thermocouple.
Step 6: Turn the knob into the on position. your furnace should now ignite.
Step 7: Turn on the furnace at the thermostat. Turn it back to the HEAT position and make sure the temperature is set to 5 degrees lower than the room temperature. At this point, there should be hot air coming from the furnace.
If the pilot will not stay lit or not light a all, call a professional furnace contractor for assistance. The thermocouple might be malfunction (which is inexpensive to fix) or there could be other problems causing the pilot light to not burn properly.
4. Check the condensate line.
Do you own a high-efficiency furnace? Is there water pooling around your furnace? If so then the condensate line (normally a PVC pipe_ on the furnace might be blocked. That can cause your furnace to shut off.
When a high-efficiency furnace is running it creates water (condensate) that then empties into a drain line, But if this line becomes blocked, the water will back up inside the furnace and cause the overkill skill switch to turn the furnace off in order to prevent any water damage from occurring.
Condensate blockages are commonly caused by:
– Ice (only when the weather is cold and the line is running through a space that is unconditioned)
In addition to blockages, a broken condensate pump can also cause condensate overflow. If this happens, a professional will need to repair the pump.
As long as the problem is not ice, unclog your condensate. If the problem is ice, wrap your condensate line with pipe insulation and heat tape.
Maintaining your furnace on a regular basis can help to prevent such HVAC problems as your furnace blowing cold air.
Regularly scheduled maintenance and cleaning can prevent many furnace problems. If you have done that this winter yet, then call us today to prevent unexpected failures and ensure your system stays in top condition.