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Why Furnance Not Reaching Set Temperature & How To Fix It

Barry Martin
June 8, 2022

We don't have any control over the weather outside, so when stepping out during winter we wrap ourselves in warm clothes to be comfortable; We can, however, condition our homes. Imagine your warm and comfortable home suddenly becoming cold and you starting to shiver because your furnace stopped working.

starting to shiver

The first question that arises is ‘Why is your furnace not reaching a set temperature with the Thermostat and how to solve it?

So, today in this blog, we will briefly discuss the reasons, solutions, and preventions of a home furnace not responding to the Thermostat.

Let's dive in.

Why is Your Furnace Not Reaching a Set Temperature

Thermostat Issues:

  • Before pondering, check if your Thermostat has any issues because your command is not reaching the furnace.
  • There can be several issues with the Thermostat. The battery you are using may be running low on power or already dead.
  • Check if the Thermostat is set in a correct manner. Set it to heat.
  • Make sure the Thermostat is not placed in direct sunlight. If it gets enough heat, then there's a possibility that it will assume you have proper warmth in your house.
  • Find a proper match for your furnace. If the Thermostat is not compatible with the system, then they'll have difficulty communicating.
  • The wires used in connecting the Furnace and Thermostat may have issues.

Tripped Breaker

If the circuit breaker is tripped, your system will not respond appropriately. Make sure the Breakers are good in condition and shape.

Also, make sure your furnace is not switched off.

Blower Problem

If your furnace is making a high-pitched sound and not working simultaneously, this indicates that the blower is not in the right condition.

Get a proper inspection and take steps to fix these issues ASAP. Wrong hands may cause more problems. For furnace inspection and repairing service, always go for professional service providers.

Clogged Air Filter

Clogged Air Filter

The air filters may get clogged because of excessive dust build-up. Clogged air filters fail to blow hot air, causing the system to not work properly.

Check the air filter and clean it or replace it to get your furnace back to its previous condition.

Backdated Software

Backdated Software

Another issue with your furnace not reaching set temperature is having a backdated software program. Smart furnaces have a software program, so if you own one, update its software on a regular basis.

Check The Panel Door

Modern furnaces have safety switches on their front panel. These switches don't allow the systems to work if the doors are not properly closed. Make sure that the panel door is secured.

The user manual may help.

Pilot Light

Gas furnaces have a pilot light in them. The pilot light gives your home furnace extra safety and ensures that the gas doesn't flow through the burners until there's a flame ready to ignite. The pilot light must be on for it to work and produce hot airflow.

This is a susceptible feature of the home furnace. Don't attempt to do anything yourself without professional help.

Blocked Vents or Registers

If the outflow vents or registers are closed, this issue will make the furnace no longer work. This is one of the common issues for air conditioning systems. Make sure the vents and the registers are not open, and there are no obstacles that may prevent them from flowing air.

outflow vents or registers are closed

Rugs, curtains, and walls may obstruct airflow or redirect the air in the wrong direction.

Contact professional cleaners and repair people to get the system fixed.

How to Troubleshoot Thermostat

inspect the thermostat device

If you face the issue of your furnace not responding to the Thermostat and want to inspect the device on your own, you may encounter these two steps below.

Remove The Cover From The Thermostat:

  • Cut off the furnace’s electricity supply from the circuit breaker panel box.
  • Remove the Thermostat's cover plate.
  • Using a Screwdriver, loosen the thermostat body mounting screws.

Examine The Wiring of The Thermostat:

  • Examine the wiring at the bottom of the base.
  • The clip, strip and reattach any loose wires or wires that have been cut or corroded to the terminal screws.
  • Replace the thermostat body plate.
  • Reconnect the circuit breaker panel box to the power source.

Although you can troubleshoot the Thermostat when the furnace is not reaching a set temperature, inspecting or troubleshooting the device without any professional help is unwise. It may get you into bigger trouble. Even if you are confident enough and really want to do it on your own, make sure you have an expert by your side.

How to Prevent Before Your Furnace Stops Responding to Thermostat:

The home furnace or HVAC system is one of the most sensitive systems in your home. So, if any issue occurs, it may cause colossal expense or suffering in the long run. So your best option is to take proper care of these systems and make sure your furnace doesn't catch any more significant issues. Prevention is always better than cure; maintenance is a must in this aspect.

First of all, go through the system's user manual and notice if there are any maintenance tips and suggestions. You'll find many. Wrong usage can result in significant harm and a great deal of suffering in the future. To keep the furnace in a healthy condition, pay attention to the maintenance instructions in the manual. Also, if the system-seller has instructed you to follow a certain procedure, do it.

Schedule Inspection with Professionals at least twice a year and fix all the issues found.

Keep your furnace neat and clean. Doesn't matter even if it's a minimal issue; fix it. Change your air filters timely, get the vents cleaned, buy a good thermostat that is compatible with your system, and always keep checking the safety features.


The problem of the furnace not reacting to the Thermostat is a common one for which people look for answers. If you're having trouble with your furnace, maybe this article can assist you in identifying and resolving any problems you're having. If you want professional help, you can always drop us a line here.

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