You walk past a vent, and the air is the polar opposite to what it should be. The vent is supposed to be letting out hot air, but instead, it’s cool. There must be a problem, and if it has nothing to do with the furnace settings, you might need to call a technician for a furnace repair. Before you pick up the phone troubleshoot the problem by checking these few items.
Thermostat. The first thing you should do if the furnace is blowing cold air is to check the thermostat. The thermostat may be set to “on” instead of “auto.” The fan works continuously in the “on” setting – heat or no heat. With the fan on the air feels cool though the room is warm. Change the switch to “auto” and the fan will only come on when heating. If the problem persists and the thermostat settings are okay, the furnace needs to be repaired.
Air Filter. Changing the air filter can quickly solve the problem. If the screen is dirty, its restricting airflow which leads to overheating causing the safety control to shut off the burners. It is a safety mechanism for the furnace protecting it from damage caused by overheating. The solution is changing the filter.
Ignition Problems. If the pilot light has a problem the furnace isn’t lighting the fuel, and this means it can’t heat your home either. Check the pilot light is on.
Insufficient Fuel Supply. If you use a gas furnace, the gas supply may be turned off, or the gas has low pressure and is not supplying adequate gas to the furnace. In this situation the furnace locks down, and the fan continues blowing cold air. Check with gas supplier.
Duct problems. If proper maintenance isn’t done on an HVAC system, leaks can develop in the air ducts. Cold air from the crawlspace enters the duct through these holes, and the vents circulate cold air making it feel like the furnace isn’t working.
Drain Line. There are modern high-efficiency furnaces that have a condensate drain line. The line removes water formed during the heating process, and if it gets clogged, switches are triggered that turn off the burners and prevent them from lighting.
Once you have checked these items and the HVAC system still has a problem, the best thing is to contact an HVAC service and repair company.