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The Daily Insight

How can you tell if your furnace is broken

Author

Sarah Silva

Updated on April 06, 2026

The furnace may cycle on or off, causing an uneven or inconsistent flow of heated air. This can be because of a poor blower or a clogged furnace filter. If you don’t feel any moving heated air or detect any unusual odors or smells coming from your heating vents, that’s a sure sign of a broken or malfunctioning furnace.

How do I know if my furnace is broken?

  1. Your Carbon Monoxide Detector Keeps Going Off.
  2. Your House is Not Warm Enough.
  3. Your Heating Bill Suddenly Goes Up.
  4. Your Hear Banging or Gurgling Noises.

What would cause a furnace not to come on?

The Pilot Light (Faulty Ignition Sensor) The pilot light or ignition sensor is usually the most common issue when your furnace will not ignite. … Put the front panel back on, turn on the gas, and then turn the furnace back on. Turn up the temperature on your thermostat to see if your furnace will now fire up.

Is my thermostat or furnace broken?

The most common signs of a broken thermostat are: The thermostat display is off or is non-responsive when you try to adjust it. The display on the digital screen is faded or incomplete. The furnace or air conditioner does not respond when you adjust your thermostat.

How much does it cost to replace a blower motor on a furnace?

On average nationwide, a furnace blower motor replacement costs $400-$600, including parts and labor. A single-speed blower motor costs around $450 to replace while a variable-speed motor costs $600+.

What would cause a thermostat to stop working?

There simply may not be any power going to your thermostat. This could be caused by a poor connection, blown fuse, dead batteries, or a tripped circuit breaker. If all of these areas look good and your unit should be receiving power, the issue lies elsewhere.

What are signs of a bad thermostat?

  • #1 – Temperature Gauge Reading Higher (or Lower) Than Normal.
  • #2 – Sudden Air Temperature Changes Inside Vehicle.
  • #3 – Coolant Leaking.
  • #4 – Rumbling Noises.
  • #5 – Heater Malfunction.

How long do furnaces usually last?

THE AVERAGE FURNACE LIFESPAN A well-maintained furnace can last at least 15 to 20 years, but completing annual maintenance and being diligent with repairs can extend its life even longer.

How much does it cost to replace a thermostat?

National Average Cost$229Minimum Cost$80Maximum Cost$450Average Range$142 to $346

Can a bad thermostat cause furnace not to work?

Malfunctioning thermostat: A faulty thermostat can lead to problems with the fan or comfort levels. The furnace doesn’t heat at all: A furnace that doesn’t perform its main task may have problems with the thermostat setting, power, gas or the pilot light.

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How do I know if my furnace blower motor is bad?

  1. Poor or Airflow from Air Vents. This will be the first and most obvious sign your blower motor has a problem. …
  2. No Airflow At All From Vents. …
  3. Skyrocketing Energy Bills. …
  4. Strange Noises When You Turn on the Heat. …
  5. Overheating Blower / Weird Smells.

What happens when your blower motor goes out?

You might also hear ongoing whirring noises, or noises that change or get louder if you increase the fan speed. These are all signs of problems with the blower motor. In some cases, you may even notice smoke or smells of burning while driving, in which case you should pull over immediately.

What can cause a blower motor to stop working?

In most cases, a blower motor resistor fails due to corrosion or overheating. Sometimes, the mechanical resistance to the motor rotation causes an excessive electric current that can overheat and prematurely damage the blower motor resistor.

How do I check if my thermostat is working?

Start your car’s engine and allow it to idle. Look through the radiator filler neck to see if the coolant flows. At this time, it should not be flowing as your car has not reached the operating temperature to cause the thermostat to open. If you find the coolant is flowing, it means the thermostat valve is open.

How do I test my furnace thermostat?

  1. Step 1: Reset the thermostat lower or higher. …
  2. Step 2: Make sure the thermostat is ON. …
  3. Step 3: Check the wiring. …
  4. Step 4: Turn breaker back on. …
  5. Step 5: Reexamine wires. …
  6. Step 6: Wrap wires together.

Do you need an electrician to change a thermostat?

Your best option is to have a C-wire properly installed and run to your new thermostat, which means it will require an electrician’s expertise. Even if you find a DIY article or video online, the risk to your health or home isn’t worth it when dealing electrical wiring.

Can I replace thermostat myself?

Can I do it myself? An experienced DIY-er can install most programmable thermostats and some smart thermostats. … If you’re replacing a central air conditioner or heating system, consider a thermostat upgrade at the same time – find a unit that will work with your family’s habits to save you the most.

Is replacing a thermostat easy?

Upgrading to a thermostat that automatically changes the indoor temperature setting is fairly easy, and it can trim about $180 off your annual heating and cooling costs, according to the EPA. Simple models that only control heat are sold at home centers for around $25.

How much does it cost to replace furnace?

How Much Does a Furnace Cost? A new furnace costs $1,500 to $6,500, depending on the model you choose. The average cost of installing a mid-efficiency furnace is $1,500 to $2,500. Mid-efficiency furnaces have an annual fuel utilization efficiency (AFUE) rating of 80% to 89%.

What does a new furnace cost?

The average cost of a new furnace ranges from $2,000 to $7,000 with most homeowners paying around $3,900. Furnace prices may vary depending on factors like brand, cost of installation, and size of your home.

How much does it cost to replace gas furnace?

A furnace replacement costs $2,000 to $5,400 on average for a new home furnace and installation labor. A gas furnace replacement costs $3,300 to $6,900 for a high-efficiency heating system. New furnace prices depend on the system size, efficiency, brand, fuel type, and install labor. Most furnaces last 15 to 30 years.

Why is my furnace blowing cold air?

Your furnace may be blowing cold air because the filter is too dirty. A dirty air filter blocks airflow over the furnace’s heat exchanger, causing it to overheat. When overheating, your furnace can trip a high limit switch, causing the furnace burners to shut off so that the heat exchanger does not crack.

How much does a furnace cost for a 1500 square foot house?

For example, a 700- to 1,500-square-foot home will require a BTU rating between 40,000 and 60,000, which will cost between $2,000 and $3,000. A furnace for a home ranging in size from 2,000 and 5,000 square feet will need between 125,000 and 150,000 BTUs and will cost in the neighborhood of $3,300 to $6,500.

What does a bad blower motor sound like?

A defective blower motor will make a continuous sound noticeable by the passengers in the vehicle. It can manifest as a knocking, whirring, clunking, vibrating, squealing, or whining noise that persists until the blower motor is replaced.

How do I know if my furnace fan is working?

Start by turning the furnace off, turn your thermostat to “fan only,” and wait a few minutes. If you see or hear the fan turn on, your blower motor is not the culprit. If the fan does not start, you have a wiring issue (circuit breaker trips) or motor problem (circuit breaker does not trip).

What happens when furnace capacitor goes bad?

A faulty capacitor might cause the furnace to become too hot internally, tripping a safety switch. If that happens, expect the furnace to shut down temporarily. If the blower runs slowly or becomes hotter than expected, it’s letting you know the capacitor is not holding its charge.

How do I know if my fan motor is bad?

  1. The fan won’t start even though the AC is on.
  2. The fan won’t stop, even when you shut the AC off.
  3. The fan turns on, yet the blades are rotating very slowly.
  4. There’s a rattling noise coming from the condenser unit when the fan is turned on.

Can a bad thermostat cause no heat in house?

HVAC system won’t turn on: The most obvious sign of a bad thermostat is that the HVAC system in your building won’t turn on or respond to the thermostat. … This results in ineffective heating and cooling and means that your indoor environment will not be comfortable.