Furnace Will Not Turn On With Thermostat

woman feeling cold at home checking the thermostat and furnace not heating

When the cold weather creeps in, people rush to their thermostats for comfort. With the press of a few buttons, the furnace will turn on and begin its heating cycle. Heating systems, like furnaces, are reliable; however, problems may arise. A common one is when a furnace will not turn on with thermostat. This is not a good situation to be in, especially in the middle of the cold season. This article includes several reasons this HVAC problem occurs and how it can be resolved.

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Why Won’t My Furnace Turn On With The Thermostat?

Regular furnace maintenance can prevent any unpleasant surprises. Yearly visits from HVAC professionals are usually scheduled in the fall to ensure your furnace is ready for hard winter. They will conduct a thorough furnace inspection for potential problems, such as excessive dirt, safety hazards, wear and tear, and imminent failure. Taking care of these issues immediately means the furnace will likely work as it should. If your furnace hasn’t been professionally maintained yet and it isn’t turning on, it may be because of the following:

Furnace Thermostat Issue

image of a woman adjusting thermostat depicting furnace wont turn on with thermostat

The thermostat is your heating system’s command center. Therefore, it is logical that you start with the thermostat when troubleshooting. If the setting you entered isn’t getting through, you may have a failing thermostat. This can be due to several reasons, including:

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Thermostat Not Receiving Power

If the thermostat setting is correct, check elsewhere. The problem may be because of power, more specifically, the lack of it. The thermostat may have a dead battery, so replace them with fresh ones and try again. Your furnace may turn on right away after this. If it doesn’t, you may have a faulty power circuit. Have an HVAC professional diagnose this issue, and provide you with professional recommendations.

Incorrect Thermostat Settings


Machines are designed to follow commands. Check your furnace thermostat settings if it isn’t working as you intended. For instance, the thermostat may have been set to OFF or COOL. Set it to HEAT if you want it to generate warm air. Take a look at the exact temperature setting as well. It may have been too low to cause any noticeable difference. Consider raising the temperature by five to ten degrees and see if that makes any difference.

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Wrong Thermostat For Furnace

There are various makes and models of thermostats. They only work with compatible systems. If your thermostat doesn’t match the heating system’s capacity and capabilities, your system may operate at a sub-optimal level. The thermostat and furnace may also miscommunicate, leading to frequent failures. Conduct extensive research or consult a professional HVAC technician before buying and installing a thermostat.

Bad Furnace Wiring

bad furnace wiring

Power and command signals pass through a network of wires. These wires can suffer from damage, such as coming loose or getting frayed over time. Bad furnace wiring can sever the link between the heating system and the thermostat. This is a common issue that shouldn’t be neglected. Homeowners who know about wiring should conduct annual inspections. They can also hire HVAC professionals to do this as part of the yearly furnace maintenance.

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Clogged Air Filter

Air filters capture airborne debris so your system can have a longer lifespan, and you can enjoy better indoor air quality. Replace your air filter when airflow becomes severely compromised. Otherwise, the efficiency and performance of your system will plummet. The strain may also cause furnace shutdown. Make it a habit to check the filters once a month and change them as needed. Buy compatible filters in bulk so that this task becomes easier.


Furnace Belt Or Blower Problem

The furnace may be working, but other problems may give you the impression that there’s a major issue. For instance, there is a high-pitch noise coming from your blower. The solution may be as simple as needing a fresh application of lubricant or replacing the worn-out belt. Other times, the blower needs to be completely replaced. Leave it in the hands of HVAC professionals to ensure a lasting and effective solution.


Furnace Fuel

Even if all furnace components work correctly, they may not be able to generate heat if there is insufficient fuel coming in. Therefore, you should check the oil or gas supply. The troubleshooting process for this is as follows:

  • Heating Oil Tank or Propane Tank is Out of Fuel: Propane and heating oil are stored on your property via tanks. Call your delivery company for a refill before the fuel level gets too low. Track your household’s fuel use patterns so you know the amount of fuel you need and when you need to get a refill.
  • Issues with Natural Gas Supply: If you have another appliance, such as a water heater or stove, that uses the same fuel, see if it still works to determine if you have a supply issue. Call the fuel company to help you in case of a supply interruption.
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Tripped Furnace Circuit Breaker

circuit breaker

Heating oil, gas, and propane may power your furnace. However, some of the system components rely on electricity. The circuit breaker protects your system from anomalies like power surges. This component may be the reason for a heater that suddenly stopped working. Check the breakers connected to the system to see if they are in good condition. Look for the furnace switch as well. Ensure it is in the correct position, as accidental movements may have switched it off. Return it to its correct setting if this is the case before trying again.

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Check the Furnace Drain Pan

HVAC systems can remove the moisture from the air, lowering indoor air humidity. The water is collected in a drain pan and automatically drained outside. However, this channel may clog, keeping the water from properly flowing. The water pump may also fail to move the liquid, keeping the pan filled with water. As a result, the float switch is triggered, preventing the furnace from turning on. The drain pan needs to be emptied so the water pump can work correctly and prevent furnace rust from occurring.

Furnace Pilot Light

image of a heating system depicting a furnace pilot light and furnace fuel supply issues

Many heating systems won’t switch on if the pilot light is out. It can go out because of system issues, drafts, or a tripped failsafe. Furnace ignition cannot occur without a pilot light. You can try relighting it, but make sure you follow the manufacturer’s manual regarding how to do this task. A few simple steps are typically all it takes to relight it. First, detach the access panel and find the pilot light assembly. Switch off the reset switch and wait 10 minutes before turning the switch to PILOT so the fuel can flow. Use a match to relight it quickly. Call an HVAC technician for professional assistance if the problem persists.

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Thermostats should be able to control your heating systems without a hitch. If you have an unresponsive furnace, go through the list above to determine the issue. The best approach to take is to consult HVAC professionals so you can save time and effort. Their expertise can help you better understand the problem and have it resolved. This way, your furnace and thermostat go back to normal immediately.

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Lawes Company has a longstanding reputation for supplying reliable HVAC repair services throughout Monmouth and Ocean Counties, New Jersey. Our technicians are the very best and thus, they are able to perform replacements, tune-ups, repairs, and installations for your HVAC needs. They are knowledgeable and boast ample amounts of industry experience.

Get the most competitive prices on HVAC services locally from Lawes Company. Experience greater home comfort, lower energy costs, and higher levels of energy efficiency with our HVAC maintenance support. If your HVAC system needs a repair or if you want to replace this equipment, we will help you find the right products for your budget and your home. Our work always comes backed by a reliable guarantee. For a service appointment, call Lawes Company. Getting an in-home estimate from us won’t cost you a thing.

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