There’s nothing worse than getting home at 6:00 at night from a long day at work and turning up the heat only to discover that all your furnace seems to do is blow cold air out of the vents. So you go to the thermostat and examine it to make sure you have it set to heat and that the temperature is set high enough (you have and it is). You turn it up even higher in hopes the furnace will finally start warming that cool air blasting from those vents, to no avail. Bummer! Now the question is: should you call a furnace repair company after hours, or try to bundle up and make it through the night. Ugh! Not the way you had imagined the evening going.
So what’s going on? Why is the air blowing from the furnace not warm? Is there anything you can try to get the furnace going?
Generally, when you have a furnace that is not blowing warm air from the vent, it’s because the unit is in a safety mode. The air is blowing because the furnace control board has told it to blow air as a precaution for one main reason: a high temperature sensor has told the control board that it has exceeded its acceptable temperature range and the blower needs to come on to cool things down. The unit will not try to ignite the flames again until the control board has been reset.
So, how do you reset the furnace control board?
Not so fast! First you must try to determine the reason the high limit switch was triggered. Often, the high limit switch in the furnace is triggered because of a lack of proper air flow and lack of proper airflow is very often caused by dirty return air filters.
As those filters collect dirt throughout the months, less air can travel through them. Because less air can travel through them, less air passes across your heat exchanger. If less air blows across you heat exchanger, your heat exchanger will get hotter than it was designed to. As a result, your high limit switch will be triggered. When they high limit switch is triggered the blower comes on at high speed to cool things down.
Sometimes, return air vents are being blocked by furniture, like a couch for instance. Yes, I understand, it was a poor design to put the return air vent right where the couch or dresser or what-have-you is supposed to go, but it’s very important that there be enough room for that return air vent to have plenty of room to breath. After all, that’s exactly what you HVAC system is, “a breathing machine.”
So before you call a furnace repair company, try these steps if your furnace is not blowing warm air. You will save a few dollars and more importantly, avoid a cold night.
First make sure all you return air vents have enough room to draw in plenty of air. Then check your air filters. Have you changed them in the last 30 days? Change them, and remember, under no circumstances should you ever run the unit without a filter in it. Even if it’s just to run to the store to buy new return air filters. Those filters are protecting an evaporator coil. If the evaporator coil gets clogged with the dirt the filter was supposed to catch, you will be in for a system that will not perform properly until the evaporator coil is properly cleaned. That is generally not a DYI job.
Okay, so you found a very dirty filter you haven’t changed in a year and you pulled the couch off the wall a few inches now what?
Go to your circuit breakers and locate the one that controls the power to your furnace and turn it off for 10 seconds, then flip it back on. Go back to your thermostat and make sure you have it set to heat and give it about 5-10 minutes.
If everything came on and you are experiencing the joy of warm air coming from those vents, congratulations! You have successfully fixed your own furnace issue and saved some money! You will be warm tonight!
If your furnace is still not performing as it should, then don’t hesitate, call Cool Change Heating and Air and we will get you warm fast!