Why is my furnace not kicking on automatically?

Author: Dr. Deja Nikolaus PhD  |  Last update: Tuesday, June 17, 2025

Check your circuit breaker panel to make sure all switches for your HVAC system are set to “ON.” Check Your Thermostat: If your furnace doesn't turn on automatically, the thermostat may have lost its programming or reset. It may even simply be set on the wrong setting.

Why wont my furnace kick on by itself?

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.

Why won't my heat turn on on my auto?

First step is to check that it is set to “HEAT” as well as “AUTO” rather than “FAN”. If your thermostat cannot detect whether the room has reached the desired temperature, it will not turn on. Next step would be to make sure that none of the wires are blocked or damaged.

Why is my thermostat not kicking my furnace on?

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.

Why is my furnace not blowing air on auto?

A dirty or clogged air filter is one of the most common culprits for a furnace running without blowing air. Importance of Clean Filters: Air filters trap dust, debris, and allergens, ensuring clean air circulates through your home.

The Most Common Reason Why A Gas Furnace Won't Turn On

Why is my furnace not turning on when I set to auto?

If your furnace doesn't switch on, the circuit breaker could be shut off. Check your circuit breaker panel to make sure all switches for your HVAC system are set to “ON.” Check Your Thermostat: If your furnace doesn't turn on automatically, the thermostat may have lost its programming or reset.

How do I get my furnace to kick on?

If nothing's happening when you're expecting the whir of a blower, check the circuit breaker and fuse. At your electrical panel, make sure all switches related to the HVAC system are on. Reset any tripped breakers and replace all blown fuses, and your furnace should kick back on.

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.

Why is the auto setting on my thermostat not working?

The most common cause of auto settings problems is software failure. The thermostat uses software to regulate heating and cooling. If the system's software is glitching, chances are the auto settings feature won't work. Other settings will be affected by this problem too.

Why is my thermostat not sending signal to my furnace?

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.

Why is my furnace fan not turning on automatically?

Inspect the Wires in Your Furnace

If your cables are looking fine, try unplugging the fan for a few minutes and then plugging it back in again. Sometimes, this process can reset the motor and solve your furnace problems. If unplugging and plugging your fan back in again doesn't work, check the fuse box.

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.

What tells the blower motor to turn on?

The thermostat is what tells these separate systems to work together. In normal operation, when your thermostat is set to "auto," it will tell the blower fan plus the heating or cooling components to turn on and off at the same time when the desired temperature is reached.

Why is my heat not turning on with my thermostat?

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.

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.

How do I know if my thermostat is bad?

7 Ways to Tell Your Thermostat Is Broken
  1. The Thermostat Has No Power. ...
  2. The AC or Furnace Won't Turn On. ...
  3. The Heater or AC Won't Turn Off. ...
  4. The Thermostat Reading Doesn't Match the Room Temperature. ...
  5. The Thermostat Doesn't Respond. ...
  6. The HVAC System Is Short Cycling. ...
  7. The Thermostat Forgets Programmed Settings.

Why is my furnace not working on auto mode?

Check the Furnace's Power Switch

If the circuit breaker is functioning correctly, inspect the on/off switch for the furnace. This switch looks like a typical light switch and is usually located directly above the furnace or on a nearby wall.

Why is my heat not working on auto?

Common Car Heater Problems

In 90% of the cases, car heater problems are the result of one of the following reasons: The heater switching system might be faulty. The cabin air filter might be choked, restricting the airflow through the heater core. The thermostat valve might not be working right.

Why wont my thermostat kick on?

No power: If the thermostat isn't working at all, there could be a power issue. Try checking the circuit breaker box or replacing the batteries. Bad wiring: The thermostat may be unresponsive if the wiring has gone bad. Remove the cover and check inside for loose, detached, or corroded wires.

Why is my furnace not kicking on?

The cause of your furnace not blowing hot air could be the thermostat configuration, a dirty air filter, the high limit switch, a clogged condensate line, insufficient fuel, leaky ducts, ignition problems, a blocked burner, flame sensor issues, gas valve malfunctions, a cracked heat exchanger, or a clogged coil.

What turns on first in a furnace?

The first motor to come on will be the inducer motor.

Not a large motor by any means, but it's the one that gets rid of the fumes spent by the flame that warms your home. The control board and a pressure switch acknowledge that the inducer has come on and is working properly.

How to reset furnace thermostat?

There is usually a small reset button somewhere on the thermostat. Finding this button may require that the thermostat panel be removed and pressing this button may require something like a paperclip to push. Hold the reset button down for 5 seconds and the thermostat should reset.

Why wont my furnace turn on right away?

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 is my furnace not responding to the thermostat?

Some common problems with the AC or furnace that can create a thermostat problem include a bad blower motor, freon leak, or leaky ductwork. With your furnace, you may find it blowing cold air, leaking, or at the very worst not turning on at all. There are multiple factors at play when you have a thermostat issue.

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.

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