Furnace not heating the house? There are a few things you can check while waiting for a repair person to show up. It’s important to keep the house warm, your health and that of your family depends on the warmth a furnace provides, particularly in the cold of winter. First of all, make sure that someone has not in advertently turned down the thermostat , as obvious as it may seem. Turn the thermostat’s temperature dial up about 10 degrees above your normal setting and give it minutes to see if it the heat comes on again.
Also, if your furnace relies on electricity, make sure the power has not gone out all over the house; there is not much that a furnace repair person can do in that case, you’ll just need to wait until the power comes back on and keep warm the best you can in the meantime.
The power may also have just gone out for the furnace, due to a blown fuse or circuit breaker, so check for that too, replacing fuse with the correct size or resetting the circuit breaker switch if necessary.
If you have an oil burning furnace, check the level of oil in the tank. Oil delivery companies generally have a policy of trying keep at least some oil in their customers tanks at all times, but occasionally tanks do run dry.
Your oil burner has a reset button which you may need to press if the safety relay switch has been tripped; only try pressing it once, though, since the button loads oil into the furnace as part of the manual restart process, and you do not want excess oil in the burner when the furnace eventually starts.
If your furnace is forced air heat, check the fan belt. Even if the furnace is running, if it has a loose or broken fan belt, the fan will not be able to effectively push air through your heating system. To check the belt, turn off power to the furnace and test the belt by pushing against it, it should give a little but not too much. You may need to replace it, or if you’re lucky, the belt will have slipped off the drive shaft and you just need to put it back on.
Make sure you get the exact replacement belt; have your furnace make and model number with you, and bring along the old belt just to make sure.
If you have hydronic heating, the water in the lines might have an excess air. In this case, you can try bleeding the radiators.
On steam heat systems, you should check for low water level. Let the boiler cool down, the check the water gauge, the gauge should be at least half full. If not, add water.
Check the pilot light on your gas furnace to see if it has gone out. If it has, then turn off the gas supply and let the combustion chamber clear itself of fumes. There should detailed instructions on how to relight the pilot printed on the furnace, which should be carefully followed to relight the pilot. It should go without saying, but never smoke or have a lit candle in the vicinity when working around your gas furnace.
If you’ve gone through all the above and still the heat is not working, you will have to wait for repairs to be done by an appliance tech. Although today’s furnaces are built to last many years, here are a lot of things that can go wrong, and diagnosing and repairing one that is not heating can be tricky. In the meantime, have all the house’s occupants stay in one room of the house, closing off all doors, or go to a friend’s or neighbours home if you can.