What Should You Do If Your Heating System Won’t Turn On

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When the heating system won’t turn on in your Indianapolis home, you might feel panicked, especially on a cold winter’s day. There are many reasons that can cause this issue, some of which you can solve yourself without a call to a professional HVAC technician. Troubleshooting can get your furnace or heat pump working properly without a service call in certain cases.

Williams Comfort Air shares the steps you need to take anytime you experience this problem with your heating system (and many work for your air conditioning unit, too). Before you call us for heating help, run through these tips that could potentially get your heater to turn on quickly, so you don’t have to wait for system services.

1. Thermostat Power Problem

In order for your furnace to run, the thermostat must have power – it is responsible for signaling the heating system. Some thermostats use batteries while others are wired into the home’s electrical system. You’ll need to check your thermostat to determine if a power problem is the cause of your heating issue, then try these troubleshooting steps.

  1. Check your thermostat display – if it is turned on but the display is blank, you likely have a power problem.
  2. Change the batteries in the thermostat if battery powered. If you have a hardwired thermostat, check your home’s circuit breaker box. Make sure the circuit breaker controlling power to the thermostat has not tripped; reset it if necessary.

2. Wrong Thermostat Settings

Sometimes when a furnace won’t turn on, it’s a simple issue with the thermostat settings. Its temperature settings might be telling the heater one thing when you expect another, which is one of the reasons a heating system won’t turn on and send heat to the home.

  1. Ensure appropriate settings are selected – the thermostat should be in HEAT mode, and the set temperature a few degrees above the current room temperature, which should trigger the furnace or heat pump to turn on. Make sure the HOLD or VACATION mode feature is not in use. Verify the programmed settings are correct for the household schedule and time of year.
  2. Sometimes, programmed settings prevent the furnace from turning on at certain times of the day. If you need to override the settings (such as for a sick day or day off work), use the thermostat HOLD feature to temporarily pause the programmed temperature schedules and adjust the heat as you like. Remember to turn the HOLD off when you want programmed temperature schedules to resume – running the heater with the HOLD feature on your thermostat for long periods will likely increase your heating costs, as most homeowners set back temperatures to create energy savings during the day when the home is unoccupied.

3. No Power to Furnace

Every furnace and heat pump needs electricity to operate, and natural gas furnaces require a working connection to the natural gas utility supply. If your heating system won’t turn on, there could be an issue interrupting the power or fuel supply to your equipment.

  1. Check the circuit breaker box in your home to make sure the circuit breaker controlling electricity to your furnace or heat pump and air handler is not tripped. If it has tripped, reset the circuit breaker.
  2. Your heating unit has physical on/off switches on or near each unit. Check these to make sure they have not been accidentally flipped.
  3. The fuse inside your furnace could have blown and needs to be replaced.
    1. Turn off electrical power to the furnace at the circuit breaker inside your home.
    2. Open the access door to your furnace’s circuit board and find the fuse.
    3. Remove the fuse and inspect it. If the fuse appears burnt, it needs to be replaced.
    4. Replace the fuse with a like fuse of the same amperage.
    5. Close the access door, turn the power back on, then adjust the thermostat to see if the furnace is working properly.
    6. If the fuse continues to blow and the furnace still isn’t working, there is a short somewhere in the system – it’s time to call a professional HVAC technician to diagnose the issue and make the needed repair.
  4. If you have a natural gas furnace, the gas valve may have been closed. The valve handle should run parallel to the gas line, indicating that the valve is open – turn it to the open position if the handle is perpendicular to the line. It’s a good idea to also check if there have been any disruptions to your natural gas utility service that may prevent gas from reaching your furnace. If someone in your home has shut the natural gas line’s valve, reopening it is a simple fix. However, a problem within your furnace might also cause the valve to close. Issues with the pressure switch, draft inducer motor, or the circuit board could cause this issue and repair will be necessary, so call your technician.

4. Loose Access Door

Many furnace and air handler models have a safety feature where they will not operate if their access panels are not secure. This safety feature is meant to prevent accidents and damage to interior components.

If Your Furnace Does Not Ignite

Does it seem like your furnace will turn on, but it’s not creating any heat? If you hear the blower running but there is not heat inside your home, an ignition problem is likely.

Pilot light out

Many older furnaces still use a pilot light ignition, which can go out due to drafts or another system issue. When the pilot light is out, natural gas is not ignited to create heat as a safety feature. To relight your pilot light, check your furnace owner’s manual for instructions, as each unit can have differences. The general process to relight a pilot light is as follows.

  1. Remove the access panel and find the furnace pilot light assembly inside. Locate the reset switch and turn the switch to the OFF position.
  2. Wait 5-10 minutes to allow any natural gas in the area to dissipate so it will not ignite once the pilot light is back on.
  3. Turn the switch to the PILOT setting, which allows natural gas to flow. Hold in the reset switch and use a match or lighter to relight the pilot light by holding the flame to the opening. Keep hold on the switch until the pilot light flame burns steadily.
  4. Release the switch and watch the pilot light. If it goes out again, check for drafts that could extinguish it. If the pilot light continues to go out, you need to call for repair services, as other issues with the furnace are likely the problem.

Dirty electronic ignition

In newer systems that use electronic ignition components, carbon from combustion can build up on the ignitor, which eventually stops the furnace from starting up – this usually produces a clicking noise, indicating the furnace is trying to come on but can’t. Careful cleaning can solve this issue but make sure to be gentle as these components can be easily damaged, in which case it will be necessary to replace it through a repair services call to your professional HVAC company.

  1. Turn off electrical power to your furnace, at the circuit breaker or the unit ON/OFF switch.
  2. Close the natural gas line valve to prevent fuel from entering your furnace.
  3. Remove the access panel to your furnace burner compartment.
  4. The ignitor components look like a ceramic piece that has wire connections at its ends. Use compressed air to clean off the ignitor, holding the nozzle a foot away from the components.
  5. Reinstall the panel, restore electrical power and natural gas, then turn your furnace back on.

If the ignitor is broken or damaged, repair is needed to replace the broken components before the furnace will ignite properly.

If Your Furnace Shuts Down Suddenly and Won’t Turn Back On

The reasons above are common when a furnace or heat pump do not turn on at all. Sometimes, you experience a heater working properly in your home for a period of time, then it shuts down and does not come back on. These troubleshooting measures help you repair issues that could be the source of this problem.

Dirty air filter

A dirty air filter can cause the temperature inside the furnace to rise too high. If this happens, the furnace shuts down to prevent damage to components like the heat exchanger and other parts. Check the filter and replace it if needed.

Dirty flame sensor

The furnace flame sensor detects when a flame is present while gas flows through the system. If it becomes dirty with soot from combustion, it may not correctly sense the flame and shut down the furnace for safety incorrectly, even though everything else is working properly. To clean the flame sensor, follow these troubleshooting steps:

  1. Turn off electrical power and gas to the furnace.
  2. Remove the access panel.
  3. Find the flame sensor and remove it – typically you will need a ¼-inch hex wrench to do so. Carefully slide it out, and you may need to remove the wire to access it better.
  4. Use a light grit sandpaper and rub the flame sensor rod to remove carbon and soot gently.
  5. Wipe off the sensor with a clean cloth.
  6. Reconnect wire if necessary and reattach the flame sensor.
  7. Replace the access door and restore electrical and gas power.

When Repair Is Needed

If the troubleshooting steps above don’t solve the issue and your furnace still isn’t working properly or your heat pump system won’t turn on, you need to call for repair to restore heating at home. Call Williams Comfort Air anytime, day or night, for repair services to fix your heater system. We replace faulty components and solve every type of system problem to ensure your family stays safe and warm.

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