Why wont my furnace turn back on?

Author: Dr. Ricky Nicolas DVM  |  Last update: Sunday, August 31, 2025

There are several reasons why your furnace may not turn on. The most common include a broken thermostat, gas line issues, clogged air filters, blocked ductwork, a tripped circuit breaker, and issues with the furnace itself.

Why wont my furnace kick back on?

If your furnace won't kick on when you turn the thermostat up, it could be due to a variety of reasons such as a tripped circuit breaker, a faulty thermostat, or a problem with the furnace itself like a malfunctioning igniter or gas valve. Checking these components might help you figure out the issue.

What would cause my furnace to not turn on?

Why is my furnace not kicking on when temp drops?
  • There is an issue with your thermostat. ...
  • There is an issue with the gas supply. ...
  • The circuit breaker was tripped. ...
  • You have a defective circuit control board. ...
  • Your flame sensor is dirty or your pilot light went out. ...
  • The ignitor is defective. ...
  • The condensate pan is full.

Why wont my furnace restart?

Check your circuit breakers: Reset any tripped breakers. Check your fuel supply: If you don't smell gas in the home, try another gas appliance (e.g., your stove). If it won't ignite, chances are it's a supply issue. Check your air filter: Regularly change your air filter.

How do I force my furnace to start?

Checking your thermostat is the best place to start. Make sure it's set to “heat” and that you've set the temperature higher than the current room temperature. If that doesn't resolve the problem, try switching your fan to “on” to force the furnace to start working.

Gas Furnace Won't Turn On? Nothing Happening? 8 Reasons Why!

How do I get my furnace to kick on?

Make sure that the circuit breaker panels and the furnace itself are in the ON position, sometimes a simple solution as to why your furnace won't kick on. If not in the on position, pop the breakers back into place carefully. Be sure to close the furnace door so the safety switch can activate the furnace.

Why is my furnace not responding to the thermostat?

Check the Power Source Sometimes the problem between the thermostat and your furnace is as simple as replacing the batteries. Many digital thermostats use standard batteries to power their functions. Also make sure to check there is power at the furnace as well.

What is a hard reset on a furnace?

The purpose of the reset button on a furnace is to shut it down before it can trip your circuit breaker. The need for this may arise if the furnace becomes too hot, or if there is some sort of electrical system interruption.

What would cause my heat not to kick on?

If your heater doesn't start, chances are the problem stems from having a dirty furnace. Having dirt on your blower motor or flamer sensor could render your furnace unable to perform. When the blower motor is too dirty, it won't pass enough cool air to the heat exchanger, leading to equipment failure.

Why isn't my furnace firing?

If your gas furnace initiates the start cycle but doesn't fire up, it's likely because of a faulty, damaged, or dirty ignitor/sensor. This is a very common problem — you can try to clean the sensor and replace the ignitor.

What would cause a furnace blower not to kick on?

A non-working furnace fan typically stems from electrical issues, mechanical failures, or control problems. Start troubleshooting by checking your circuit breaker, thermostat settings, and air filter condition.

How do I know if my furnace is broken?

Warning Signs That You May Need A Furnace Replacement
  1. 1 – Frequent Repairs. It's not abnormal to need furnace repairs once a season. ...
  2. 2 – Cold Air. ...
  3. 3 – Strange Noises and Odors. ...
  4. 4 – Yellow Pilot Light. ...
  5. 5- Increased Dust. ...
  6. 6 – Increased Heating Bills. ...
  7. 7 – Poor Temperature Control.

Why won't my HVAC unit kick on?

It Won't Turn On

Check your breaker box for a blown breaker or tripped fuse. You may be able to fix this AC issue with the flip of a switch. If that doesn't do the trick, check the wiring in your thermostat. A loose or frayed wire could also prevent your unit from turning on.

Can a thermostat cause a furnace not to work?

Thermostat issues are one of the most common culprits of furnace malfunctions. If your furnace isn't working as well as it should, and you've determined that other issues such as a faulty furnace heat exchanger or dirty air filters aren't to blame, you should inspect and troubleshoot your thermostat.

How do I reset my furnace ignitor?

You can reset the ignition on your furnace simply. To do this you must cut the power to the furnace first by turning off the circuit that powers it. Once the power is off you can remove the burner door to reveal the ignitor. Turn this to “off” and leave it off for at least 5 minutes.

How long does it take for furnace to turn back on?

Your furnace should start up within five minutes of you turning on your thermostat.

How do I get my heat to kick on?

What To Check If Your Heating System Does Not Switch On
  1. Replace the Batteries in Your Thermostat. ...
  2. Check the Settings on the Thermostat. ...
  3. Check the Circuit Breaker and Emergency Shutoff. ...
  4. Change the Air Filter. ...
  5. Cycle the Power on Your HVAC System.

Why is my thermostat not turning the heat on?

If your thermostat won't turn on the heat in your home, change out the batteries and see if that fixes the problem. If not, your faulty thermostat could be the result of the following: A tripped breaker. Loose wiring.

Why is my furnace not turning on?

There are several reasons why your furnace may not turn on. The most common include a broken thermostat, gas line issues, clogged air filters, blocked ductwork, a tripped circuit breaker, and issues with the furnace itself.

How do you know if your furnace needs to be reset?

Why Your Furnace May Need To Be Reset
  1. The furnace has overheated: When your furnace runs too hot, it triggers a safety shut-off to prevent damage. ...
  2. The fuel supply is empty: Your furnace can't generate heat without fuel. ...
  3. The gas valve is shut: A closed valve blocks the fuel supply.

Is it safe to hit the reset button on a furnace?

Mind the safety lock. When resetting your furnace, make sure to press the button only once to avoid engaging the safety lock. Reach out to professionals. In most cases, the safest course of action is to contact your go-to HVAC company if your furnace doesn't work after a power outage.

Why is my heat not kicking on?

Make sure your thermostat is set to “heat” and the temperature is high enough to turn on the furnace. Go to your electrical panel and check the circuit breaker. If it's tripped, reset it and turn the furnace back on. Check your furnace filter and if it's dirty replace it with a new one.

Who do I call if my furnace isn't working?

If your furnace's problems continue, contact an HVAC expert. Also, if you notice discoloration when you check the pilot light, get professional help. If there are cold spots in your home, even though hot air is coming out of the air vents, the issue could be different from your furnace not working.

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