What to Check First If Your Heater Isn’t Working

When it is close to freezing outside, the last thing anyone needs is to arrive home to a cold house when the heater isn’t working. The easiest way to prevent a heater failure is to regularly maintain your system in the fall, before the weather gets cold.

Despite your best efforts, if your furnace has left you chilly, there are a few things you can check before giving a heater technician a call that might save you some aggravation and get your heater or furnace running quicker, too.

Check the Furnace Power Switch

Some furnaces have an on/off switch that is frustratingly easy to switch off by mistake. If you store holiday decorations in an attic near your furnace, it is possible you  switched off your furnace by mistake.

If you’ve had any other technicians near your furnace, such as a cable/Internet installer, holiday lights installer, electrician, or plumber,  consider checking the on/off switch on the furnace in your attic.

Look at Your Fuse Box That Powers Your Heater

If checking your heater’s power button doesn’t solve the problem, check the power supply and see if any of your electrical breakers for your furnace have tripped. Occasionally resetting a tripped breaker can get your heater going again.

However, if the power keeps tripping off on your furnace that likely means a safety feature has been activated and it is wise to call a licensed professional to see what the problem may be. A licensed HVAC technician can tell you if it’s a power supply or safety issue related to your heater, or if it’s a larger electrical issue that an electrician will need to address. 

Heaters and furnaces have many safety measures built in, and they will power off until a professional can fix it. These safety measures exist for a reason — to keep you safe.  Here’s typical safety features most forced air furnaces have:

  • Furnace Safety Switch or Upper Limit Switch

    This safety feature detects high temperatures in your furnace and will shut it off to avoid a fire. If air flow is not working because of a malfunctioning blower motor, capacitor or control board, it is a fire hazard. A licensed HVAC technician will need to reset the system after this feature is activated.
  • Thermocouple or Flame Sensor

    This safety measure detects a weak or non-existent pilot light and will shut your furnace off to prevent an explosion.  Thermocouple version is found in older equipment; the flame sensors are found in modern furnaces. 
  • Vent Safety Switch

    This switch monitors all the flue gasses as they go through the heat exchanger and are ventilated through the top of the roof.  This switch proves that the flue gasses can be exhausted from the furnace safely. This is why the furnace will not start if this switch has activated.

    The most common reasons this vent safety switch activates can be due to bird’s and wasp nests that block the vent and even a build-up of a chalky substance that comes from the gas odorant. It’s something we clean when we do heater tune-ups. The build up of that chalky substance which is the by-product of the odorant in the natural gas we burn is a common reason for a misdiagnosis of a heat exchanger failure. 

Check the Batteries in Your Thermostat

If your thermostat runs on batteries, try replacing them. You’d be surprised how many times this simple fix gets a heater going again.

It may sound like a no-brainer, but you do need to turn your thermostat to the “heat” or “automatic” setting before your heater will click on. If you have the heat set to come on to maintain the indoor environment at 72 degrees and the thermostat is set to “cool,” your furnace will not turn on. 

Occasionally, smart thermostats can get “stuck” and need to be restarted. The easiest fix is to remove them from the wall, and reattach them to complete a manual reset. It’s similar to turning your computer on and off and takes less than a minute to do.  

Replace the Air Filters

When was the last time you changed the air filters in your home? I hope the answer isn’t years! Clogged or dirty filters can wear out the electrical components that keep the warm air blowing through your home’s air vents. They can also “choke out” your system and make it stop working. If your heater isn’t able to take in enough air, it causes problems and may cause it to overheat and shutdown.

Some homes have filters in their return air vents and some have their air filters in their furnace. We don’t recommend double-filtering unless your system is designed to handle this arrangement.

If you replace the air filter in your furnace, make sure the cover is closed correctly. If the furnace door isn’t closed, the furnace may not turn on. 

Disposable air filters are designed to be replaced regularly (every 1-3 months). Do yourself a favor and change the filter if it has been longer than 3 months. We have an easy tutorial that shows you step by step how to change your air filters.

Notice Any Odors

If your heater isn’t working, you shouldn’t smell anything in the air. If you smell a burnt or smoky smell or a gas-smell, that can be a worrisome sign and you should get professional help quickly. 

Note that if you have a carbon monoxide leak, you won’t be able to detect that on your own, which is why we recommend the installation of carbon monoxide detectors and smoke alarms in every home. This is particularly important for gas-fired furnaces because combustion produces carbon monoxide, which is an odorless, poisonous gas.  If your carbon monoxide alarm goes off in your home, get everyone out of the home and call the fire department. 

Heater Isn’t Working? We Can Help Keep You Toasty!

Call the experts at Terry’s Air Conditioning & Heating at (281) 495-7830 to get on our schedule for an HVAC service call in the West Houston, Richmond, Katy, and surrounding area. We can inspect and maintain your heating system to eliminate surprise failures, which inevitably come at the worse time possible. Whether it’s a clogged vent, pilot light problem, or a faulty motor, we can get your furnace, heat pump, or electric heater up and running in a jiffy. Find out more about what customers have to say about our heating repairs, and find out what a difference it makes to hire a family-owned company that wants to be your “Your Personal Indoor Comfort Concierge.”