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Furnace problems – what to check first

6 things to consider checking before you call.

Many furnace issues can be fixed with some basic checks first.

1. Make sure your furnace is getting power

Check your fuse box for any tripped circuit breakers, especially since this could indicate a bigger problem with your electrical system.

2. Ensure that the furnace power switch has been switched "On"

Since furnaces can be tucked into tight, confining spaces or closets, the switch can easily be accidentally switched "Off". Look for the power switch mounted on the side of the furnace. It may also include a liftable metal housing containing a fuse. If the fuse is blackened and burnt, then it will need to be replaced. However, remember that a blown fuse may also indicate a bigger system problem, so the system should be inspected by a licensed technician.

3. Look outside to make sure that nothing is blocking the fresh air intake and the exhaust

Not all furnaces vent through chimneys. Many newer furnaces have their fresh air intakes and exhausts run through the side of the home and sometimes windblown leaves, insects, and moisture affect heating systems. If this is the case, you might want to consult a licensed technician about possible venting solutions.

4. Check your thermostat settings

Make certain your thermostat has been set to "heat" and that it is set to a temperature high enough for the furnace to come on. While that sounds obvious, it's a small detail that is easily forgotten by a worried homeowner. It's a good idea to keep your thermostat's user guide stored near the thermostat. That way, you can consult its troubleshooting section in the event of a start-up problem.

5. Check thermostat batteries

Many programmable thermostats feature a flashing "low battery" icon on their control screen. If you see a "low battery" warning, promptly replace the batteries with new ones.

6. Check your furnace filter

If your furnace is firing up but it's not blowing as hard as it normally does, then it might mean that the air filter needs to be changed. Air filters trap dust, hair, and other particles in the air and, over time, the filter gets so full of debris that it can restrict air flowing through your furnace system. On most residential heating systems, air filters should be changed every 3 months.


If you have tried everything and your furnace will still not start, call for a licensed technician to inspect your furnace. Newer gas furnaces are far more complex than older models so you need expert advice. Often a service technician can tell you about factors common to your furnace make and model so that you can solve them yourself in the future. They can also identify issues and repair components before they require an expensive emergency service call.

The best way to keep your furnace staying efficient and reliable is to have it inspected before you really need to use it. Before cold weather strikes, set up an appointment to have your heating system inspected by an expert. Yearly fall maintenance can save you time, frustration, and money when it's done right by a licensed technician from Enercare.

Legal notes: Read the fine print.

The contents of this webpage are provided for general informational purposes only. We do not make any warranties about the completeness, reliability or accuracy of the information as it relates to your circumstances. Any action you take upon the information provided is strictly at your own risk. This information is not a substitute for, and is not intended to replace, independent professional advice. It is your responsibility to take all safety precautions and to refer to the product manufacturer's instructions or contact a licensed technician, as appropriate.