Why Won’t My Furnace Turn On?

  1. Woman adjusting thermostat

Each year, especially at the beginning of the heating season, we receive quite a few calls from local homeowners asking, “Why won’t my furnace turn on?” We understand how frustrating it can be when your furnace won’t turn on and you’re wracking your brain to figure out what could be the problem. Mission Mechanical covers some of the most common reasons a furnace won’t turn on, and what to do to troubleshoot and fix the problem.

Check Your Furnace’s Power

Power problems are a leading reason behind why furnaces won’t turn on, especially after it hasn’t been used in a while. The first thing you need to do is to make sure that it has power. Even natural gas or oil furnaces use some electricity to operate, so check the breakers to your HVAC system and reset them if needed.

The furnace will have an ON/OFF switch located on the equipment cabinet or nearby, likely on the wall. Make sure the switch is in the on position. If it’s in the off position, turn it on and wait for the furnace to start up.

Check Your Furnace’s Pilot Light

It’s possible that your furnace isn’t working because the pilot light is out. Some older furnaces have a constantly burning pilot light inside that ignites fuel when the system turns on. If the furnace pilot light goes out, the gas furnace will not work.

If you’re not sure how to check the pilot light, or if it’s out, open the access panel to inspect it. If it is out, follow the owner’s manual instructions to relight it, and watch to make sure the pilot stays lit. If the pilot repeatedly extinguishes or you cannot relight it, repairs may be needed.

Check Your Furnace’s Thermostat

Thermostat issues are often behind furnaces issues, at the beginning of the cold season or throughout it. If your furnace isn’t turning on, the first thing you should do is check the thermostat. Make sure the thermostat has power by replacing batteries or checking the circuit breaker. If it doesn’t, your furnace won’t turn on no matter what you do, as the thermostat is responsible for communicating with the furnace to tell it when to start and stop.

If the thermostat is powered on and functioning properly, make sure the mode is set to HEAT and the temperature is set a few degrees warmer than the current room temperature. If the thermostat is set properly but your furnace still isn’t turning on, there may be a problem with the thermostat itself or the wiring between it and the furnace.

Check Your Furnace’s Filter

One of the most common reasons a furnace won’t turn on, especially after a long break, is because the air filter is dirty. A dirty filter can stop air moving through the furnace so it is unable to turn on, or it can cause the furnace to overheat and shut down for safety.

To check the filter, remove the existing filter and check its condition. Replace it with a new furnace filter if the filter’s surface is entirely covered with particulate matter.

Check the Natural Gas or Heating Oil Supply

If your furnace won’t turn on, it’s possible that there is an issue with your natural gas, propane, or heating oil supply. Make sure to check the gas valve on the pipe leading into the furnace to verify it is open. You should also check the operation of other gas appliances in your home to see if there may be a problem with your natural gas supply.

If you have a propane or oil furnace, check the tank’s gauges to see if fuel is available. If the gauges indicate that there is no fuel in the tank, schedule a fill from your provider.

Furnace Repair in Indianapolis

There are a few common reasons why your furnace won’t turn on when you try to use it. These causes are especially common the first time you go to use the heating system each year, but it can happen throughout the heating season as well.

It’s important to troubleshoot the problem and find out what’s causing your furnace to not turn on. If you can’t fix the problem yourself, you’ll need to call Mission Mechanical to take a look. Our certified furnace repair technicians will find out why your furnace won’t turn on and make the necessary repairs to restore heat in your home. Contact us now if you need furnace repairs.

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