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Dealing With No Heat? Here's What You'll Need To Do

When you turn on your furnace, you expect warm air to follow shortly thereafter. But what happens if you turn on your furnace and you get cool air instead or nothing at all? You may be dealing with a problem that's leaving your furnace in the cold. Here are a few troubleshooting tips you can use to get your furnace back on track.

Check Your Thermostat

One of the most common causes of a furnace that isn't producing heat is an improperly set thermostat. Before troubleshooting the rest of your heating system, make sure your thermostat is not only set on "heat" mode, but that the desired temperature set point is higher than your home's current temperature as displayed on the thermostat. Your furnace won't run if the set point is below the current temperature.

If your thermostat is properly set but your furnace still won't run, it may be time to check how the thermostat is wired. Your HVAC technician can help troubleshoot wiring issues that result in your furnace not producing any heat.

Check Your Gas Supply

If your furnace uses natural gas or propane, you want to make sure there's enough fuel going to the furnace. With this in mind, make sure the gas supply valve is turned to the "on" position and that the pilot light is lit. If you're using propane, make sure you're not running low on the gas. You should schedule a delivery with your propane supplier if the fuel level in your propane tank drops below 20 percent.

If you smell a strong odor of rotten eggs while checking your gas supply, leave the house immediately and call your local gas company and fire department. Do not attempt to re-enter the home or shut off your gas supply.

Relight the Pilot

The vast majority of older furnaces rely on a pilot light in order to ignite the main gas burners. It's not unusual for the pilot light to be extinguished by a strong draft or problems with the pilot light's gas supply. First, check and block any nearby drafts, and relight the pilot light according to your furnace manufacturer's specific instructions. If the pilot light continues to go out, try the following:

  • Adjust the size of the pilot flame using the small set screw on the pilot valve body.
  • Remove and clean the pilot orifice with a small length of stiff wire.
  • Remove and replace the thermocouple.

Keep in mind that newer furnaces may rely on a hot surface igniter instead of a traditional pilot light. If these furnaces refuse to fire, the solution is usually as simple as replacing the old igniter with a new one.

Check Your Furnace Fan

An inoperative furnace fan can also cause a furnace to not heat properly. Without a steady flow of air provided by the furnace fan, it becomes nearly impossible to circulate the warm air generated by the furnace itself. If your furnace fan isn't working, here are a few possible fixes to explore:

  1. Replace the furnace fan limit switch. The limit switch essentially acts as a controller for the furnace fan, telling it when to turn on and off. Over time, the limit switch can fail, preventing the fan from starting when it's needed.
  2. Check and replace the fan belt drive. Older furnaces may rely on a belt-driven fan instead of the more common "squirrel-cage" blower fans. It's not uncommon for the belt to slip or completely break due to age and ordinary wear.
  3. Replace the furnace fan motor. If the furnace fan shows signs of excessive wear and tear or if it's completely burnt out, you may need to have the motor replaced.

Don't hesitate to use these and other troubleshooting tips to solve your furnace's no-heat problems. For more information, check out websites like