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With the coldest part of the winter setting in, this is the last time you want to deal with a broken furnace. You need your furnace up and running as fast as possible to keep your household warm.

There are a number of reasons why your furnace might not turn on. In some cases, you may be able to fix the problem yourself even with minimal HVAC knowledge. In other cases, you should call a professional furnace repair technician.

You may need to do a little troubleshooting to figure out what the problem is. If you’re not sure what’s keeping your furnace from turning on, here are some things you can try.

What to Do When Your Furnace Won’t Turn On

1. Check the thermostat.

This tip might seem silly or obvious, but it’s always worth checking your thermostat if your furnace won’t turn on.

  • Check that your thermostat is in the “ON” position and showing a temperature that seems reasonable.
  • Thermostats can stop working when it’s time to change the batteries. You should change your thermostat batteries once a year or as needed.
  • If you’ve recently had a power outage, your thermostat may have reset itself or gotten its heating schedule mixed up.
  • If your thermostat’s wiring is covered in dust and other debris, you may need to clean it to get it to work.

2. Check the circuit breakers.

furnace won't turn on

One of the most common sources of furnace problems is a tripped circuit breaker. Even propane and gas furnace systems can have an electric source, so it’s worth checking your circuit breaker to see if that’s the problem.

Most people accidentally trip a circuit once in a while, and you may not have noticed when it happened. Fortunately, if a tripped circuit breaker is keeping your furnace from running, that’s easy to fix!

Go to your home’s circuit breaker. If you don’t know where it is, check the basement or garage area — many homes have their circuit breakers there. You will be able to manually look inside and see whether the circuits are in the “ON” position. If one of them is “OFF”, that might be the cause of your furnace problem.

One safety note to keep in mind: you should never tape a circuit breaker to the “ON” position!

If other electrical devices around your home, like the TV and refrigerator, aren’t working, you likely have a power outage. You can call your electric company to let them know about the problem and find out when it will be fixed.

3. Check your furnace filters.

Did you know that dirty air filters can prevent your heating system from running? Your HVAC system needs airflow to start up, and a dirty filter can prevent that essential airflow.

When your heating system doesn’t get an adequate supply of fresh air, the igniter can’t produce the air mixture it needs to turn on. A clogged filter can also increase the risk of a fire. Most HVAC systems have a safety feature that will prevent the furnace from turning on when the filter is overly clogged.

4. Check the flame sensor.

This step is only for homeowners who are unusually knowledgeable about electricity. If you are an average homeowner with an average grasp on home projects, skip this step and go straight to a furnace repair professional.

If you are confident around electricity, you can look in your furnace’s operating manual to find the furnace flame sensor. Sometimes furnace functioning problems are caused by a dirty sensor. You may be able to get your furnace working again by cleaning the sensor.

5. Talk to a furnace repair professional.

furnace won't turn on

If none of the previous steps diagnosed the problem, it’s time to call in the pros. Most other furnace issues should be taken care of by a trained, experienced furnace technician.

You should also call an HVAC professional if:

  • You smell sulfur. This might be a sign that your furnace is leaking toxic, hazardous gas, so call an HVAC professional ASAP! Odd and eggy smells signal danger.
  • Your furnace is making strange noises and you can’t fix them. Sometimes a rattling furnace just means your blower motor has a loose screw. Other times, noises can be a sign of a more serious problem. If you’re not experienced with wiring or electrical fixes, you should call an HVAC pro to deal with the problem.
  • Your DIY repair didn’t fix the problem. If you’ve tried to fix a furnace problem and your furnace still won’t turn on, or if new problems have come up, it’s time to get a professional’s opinion. Call up a trusted HVAC company with a solid reputation and plenty of experience.

If you’re having trouble getting your furnace to turn on and you live in the Snohomish or East King County area, reach out to Paragon Heating and Home Comfort Solutions today. Our trained, certified, and highly experienced technicians can help you find and fix the problem.

We are proud to continue our tradition of excellence in serving homeowners throughout Snohomish and East King Counties. Our goal is to ensure your HVAC system works well and meets all your needs. In addition to furnace repairs, we also do planned maintenance and installations. Contact us today for help with your furnace.