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How to Troubleshoot
Your Furnace

How to Troubleshoot your Furnace


Your furnace is one of the most complex and important appliances in your home, so when it’s not operating at peak efficiency – or not heating at all – it can be a real problem. Luckily, there are a number of things you can do to assess and possibly correct what may be wrong when an issue comes up.

Check the Thermostat

It may seem obvious, but the first thing you should check is the settings on your thermostat. The thermostat controls when the furnace turns ON and shuts OFF, depending on the surrounding indoor air temperature. If the thermostat isn’t working or set properly, it will definitely cause problems.

  • First, make sure your thermostat is on the Heat setting. Any thermostat that’s also part of a central air conditioning system will have both a Heat and Cool setting.
  • Check to see that the thermostat is set a few degrees higher than the room temperature This is necessary to activate any furnace to deliver heat.
  • Replace thermostat batteries if your system has them.
  • If your home’s temperature regularly seems out of step with thermostat settings, look at thermostat location. A poorly located thermostat that gets false readings from other heat sources or is too close to an exterior door, can create ongoing temperature problems. If you suspect your thermostat is in the wrong place, it’s best to call an expert to have it reinstalled in an optimal location.

Check the Furnace

There are several simple checks you can do that may determine why your furnace is not coming ON or not producing enough heat.

First, check that all vents, registers and return air grills are open and free of obstruction.

If your furnace won’t turn on at all, check to see that the main furnace switch is in the ON position. This switch is usually located near the furnace on a wall. Furnace switches are typically part of the wiring leading to the furnace.

Check the electrical panel to make sure that the breaker feeding power to the furnace hasn’t tripped. Shut the breaker all the way OFF then all the way ON again to reset it.

Make sure all doors and filter access panels are fully closed. Furnaces have safety switches that won’t allow the unit to operate if the furnace doors are not closed properly.

Ensure that your furnace filters are clean and free of dust and debris. A clogged filter can cause a furnace to stop working or work poorly.

When to Call an Expert

If none of these simple checks solve the problem, call a licensed furnace professional.

Other reasons to call a professional include unusual sounds, vibrations, rattles, clicks or if the furnace seems to be straining to operate. This could be a sign of an internal mechanical problem.

If you need assistance with any furnace maintenance or repair, Call on RelianceTM.