Help!: The Thermostat Is On, But the Heat Is Not Working

The thermostat is set to the ideal temperature, but for some reason the heater just won’t come on. Sound familiar? This is a relatively common problem, and if your thermostat works but the heat doesn’t come on, you may be dealing with one of the following issues:

Thermostat Is On

A Safety Switch Has Turned Off

Furnaces made in the last 30 years feature numerous safety switches that disrupt power to the furnace in the event of a risk, and any of the following problems can cause a safety switch to turn off the furnace:

  • Grimy evaporator coils

  • Clogged pipes

  • Dirty filters

  • Exposed or unattached wires

  • Control board failure

  • Broken blower motor

  • Malfunctioning blower fan

  • Not enough pressure moving through the flue vent 

Sometimes the blower motor’s safety switch turns off due to an overload, and you may be able to resolve the issue with a reset. If the furnace is hot, give it about 30 minutes to cool down, and then, look for a reset button near the blower motor’s housing. Press the button, and see if the furnace starts working on. 

If the reset doesn’t work,contact an HVAC technician to assess the problem and get your furnace working again.

Your Furnace Isn’t Getting Power

In some cases, your thermostat may be working fine, but it cannot communicate with the furnace because the furnace isn’t getting any power. If you have an electric furnace, check the breaker to make sure it hasn’t tripped. Then, also make sure the furnace switch next to or inside your furnace cabinet is on. 

With a gas furnace, look to see if the other gas appliances in your home are working. If they aren’t, you may have a supply issue and need to contact the local gas company. If the other gas-fueled appliances in your home are working, the gas valve or control board on your furnace may be malfunctioning and unable to build a flame.

Your Furnace Needs Maintenance

If your furnace is responding to the thermostat but then turning off mid cycle, it may simply need some routine maintenance. Relatively small issues can stop your furnace from working, and routine maintenance helps you to avoid or address these problems. 

For example, when an HVAC technician inspects and cleans your furnace during a routine maintenance appointment, they help to ensure that motors can spin without resistance from built-up dirt and grime. They also make sure that gas flames can stay lit without consuming or leaking excess gas, and they monitor motors or wires for excessive wear and tear. 

If lack of maintenance is causing your furnace to be unresponsive to your thermostat, a furnace repair person can diagnose and fix the problem. Then, you can minimize the risk of future breakdowns by scheduling routine furnace maintenance about once a year. 

Is your thermostat working but your furnace won’t come on? Does your furnace stop mid cycle? Is the furnace not responding to the thermostat? Then, the culprit may be a safety switch, a lack of power to the furnace, or an issue related to lack of routine maintenance. 

Regardless of what’s happening, we have the experience to fix your furnace and get your home warm again. At N.E.T.R., Inc, we have been helping keep home and business owners in Boston and the surrounding area warm through the cold New England winters for over 30 years. Trouble with your furnace or thermostat? Then, call us today.

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