Why Furnace Not Responding to Thermostat?

You change the temperature on the thermostat, but your furnace does not seem to care about it?

When a furnace is not responding to a thermostat, there is either a problem with the heating unit or the actual thermostat. Lack of power to the thermostat, wrong settings, and outdated software might be to blame, as well as faulty wiring, a tripped breaker, and a dirty furnace filter.

Why Furnace Not Responding to Thermostat?

Thermostat Issues

  • Lack of power

The battery in your thermostat might be low or there is simply no power supply.

  • Wrong setting 

Double-check the temperature settings and make sure that your thermostat is set to ‘heat’, not ‘fan’ or ‘cool’.

  • Wrong thermostat placement

Your furnace might not be kicking in because the thermostat thinks that the house is warm enough. This might happen if you place the device in direct sunlight or next to a heating source.

  • An inappropriate device for your furnace

The thermostat and the heating system have to match. Otherwise, they won’t be able to communicate.

  • Faulty wiring

Frayed or old wires and loose connections – these things can cause the thermostat to not have a connection with the furnace.

  • Outdated software

If you have a smart device, then you would have to update its software from time to time.

Read: HVAC Thermostat Problems

  • A faulty device

Finally, the thermostat might have simply gone bad. One of the inside components could have failed completely or the device is just reaching the end of its lifespan.

Furnace Issues

  • Faulty wiring

The wires that connect the thermostat with the furnace might get damaged and the units won’t be able to communicate at all.

  • Clogged filter

The furnace might be receiving the call for heat, but it will fail to deliver the heated air if the air filter is clogged.

  • Tripped breaker

Insufficient airflow, leaky ducts, motor issues, a blocked flue, and a dirty flame sensor – all these things can cause one of the safety breakers in the system to trip and shut the whole unit down.

  • Belt or blower issue

The furnace might be receiving the thermostat’s signal, but it will not be able to deliver the heat if there is something wrong with the blower.

Read: No Power To The Home Temperature Thermostat – Troubleshooting Guide

Honeywell Thermostat Not Communicating with Furnace

The easiest thing that you can do is delete and reinstall the app (Honeywell Home App or Total Connect Comfort App) and reconnect the thermostat to the Wi-Fi.

Hint: the majority of Honeywell thermostats are compatible with the 2.4GHz band of your Wi-Fi. At the moment, T9/T10 are the only devices that are compatible with 5GHz.

You can also try to reset the thermostat to its default settings.

Read: Honeywell Thermostat Troubleshooting Guide

What Would Cause a Furnace Not to Kick On?

  • Thermostat settings
  • A tripped circuit breaker
  • Dirty furnace filters
  • A pilot light that keeps going out
  • A faulty blower motor
  • A faulty ignition switch

Can a Bad Thermostat Cause Furnace Not to Work?

The furnace won’t be able to perform to its full potential or operate at all if there are issues with the thermostat.

The device might have:

  • Power issues (dead batteries or a turned off power switch)
  • Matching issues (the thermostat is not the right fit for the furnace or has not been connected correctly)
  • Faulty wiring 
  • Dust and debris inside
  • A faulty heat anticipator (in non-digital thermostats)
  • Inaccurate readings

How Do I Fix an Unresponsive Thermostat?

  1. Make sure that the device is set to ‘heat’.
  2. Reset the thermostat.
  3. Turn off the device and replace the batteries (lithium batteries will last longer than alkaline ones).
  4. Mechanical thermostats can accumulate dust inside. Turn the device off, remove the cover, and use a soft brush to get rid of the dust.
  5. To clean the contacts, you can slip a paper between them.
  6. While you’ve got the cover removed, check the wiring (it should not be damaged) and whether each wire is connected to the right terminal.

How Do I Reset My Furnace Thermostat?

Here is how you can reset your programmable thermostat:

  1. Turn the device off.
  2. Remove the battery cover (if it’s on the back of the thermostat, you might have to take the device off the wall).
  3. Take the batteries out and then insert them backward for 5 seconds.
  4. Remove the batteries and put them back in but in a normal way this time.
  5. Turn the device on.

Some models can be reset by simply shutting off the breaker to the device for around 30 seconds.

Where Is the Reset Button on a Thermostat?

Bear in mind that the reset button might return the thermostat to the factory settings.

The majority of devices nowadays have a reset button that you should simply push. At times, you would have to use a paperclip to do that.

Make sure to hold the button for at least 5 seconds. If you hold it for less, the thermostat might just turn off.

Read: Temperature Thermostat Problems

How Do You Know If You Need a New Thermostat?

Sometimes, all you would have to do to make your furnace respond to the thermostat again is replace the device.

Here are the main signs that indicate that you need to get a new thermostat:

  • There is no communication with the furnace

If the wires are severely damaged and/or the thermostat tends to unexpectedly turn your furnace on, then it might be better to get another one.

  • The device registers incorrect temperatures

If your thermostat is located in the right place (where the readings are not affected by other sources) but is still not able to register the right temperature, then it might have gone bad.

Another sign is constant temperature fluctuation.

  • A higher than usual energy bill

Your bills will skyrocket, if the thermostat fails to read the correct temperature (this can cause the furnace to overwork) or if the device likes to randomly turn your heating on.

  • Constant temperature swings

In case the central air is not able to maintain a constant, comfortable temperature, then it might be the thermostat fault.

  • The device is too old and outdated

If you have a non-programmable thermostat, it would be better to upgrade the device to a newer model.

If your thermostat is nearly 10 years old (or over), then it, once again, should be replaced to increase energy efficiency and to improve overall performance. 

Read: Benefits Of A Programmable Thermostat

Can I Run My Furnace Without a Thermostat?

The majority of homes have thermostats that control their heating and cooling equipment.

The good news is that if your thermostat ever goes bad and fails to turn your heating system on, you wouldn’t have to try to survive in a cold house until the repairman arrives.

You can temporarily bypass the device to keep your space warm.

  1. Turn the breaker to the furnace off.
  2. Open the thermostat’s cover.
  3. Find the red and white wires.
  4. Loosen the screws that are holding these wires. Unwrap the wires and make sure to hold on to them, otherwise, they might ‘fall’ into the wall.
  5. Carefully wrap the exposed part of the wires together. You can slip, for example, a pencil behind them to prevent the wires from falling.
  6. Turn the breaker back on.

Warning! You can use this only as a temporary solution as, in such a case, the furnace will continue to run all the time, unless you manually disconnect the wires.

Read: Thermostat Wire Color Code