How to Troubleshoot Your Gas Furnace

It’s the coldest day of the year, complete with snow and blustery winds that chill you to the bone. But you’re warm and cozy indoors, with not a care in the world – until your gas furnace decides to stop pumping out heat.

Should you panic, wondering if you can get a qualified tech out asap? Not so fast. Before you reach for the phone, try these 8 troubleshooting tips to get that warm air going again.

  1. As a first step, make sure the thermostat is set to “heat”. Perhaps it was accidentally switched off.

  1. Replace the batteries but first check them in another device to make sure they work. If you’re still not getting any heat, set the thermostat to 80 degrees Fahrenheit so it won’t cycle on and off while you continue to troubleshoot.
  2. Check the filter. When was the last time you cleaned or replaced it? If you can’t remember, it’s been too long. A clogged dirty filter can either trigger the furnace to shut down to prevent damage or continue to run but with reduced heat output and efficiency.
  3. Make sure the furnace is getting power. Most traditional thermostats have a switch for the fan that reads “auto” or “on”. Flip the switch to on/auto – if the fan comes on, there’s power to the furnace. If it doesn’t, check the breaker panel to see if the circuit has tripped.
  4. If all seems well at the electrical panel, check the furnace switch. It looks like a regular light switch, often in red, and is located either on the furnace or a nearby wall. Is it switched off? Flip it back on and wait a few minutes to see if the furnace fires up. If it’s on, flip it off and back on. If that’s not the issue, keep going.
  5. Newer furnaces are often equipped with a small window that lights up to tell you the furnace is getting power. What’s more, this window can flash a sequence of lights that correlates to a key in the access panel. Once you flip the furnace switch off/on, note the sequence of lights and take note of the code. This is helpful info in case you need to call a technician.
  6. If your furnace is older, you may have to relight the pilot light. The owner’s manual has instructions on how to do so, but please don’t attempt this unless you have the knowledge and comfort level to proceed.
  7. Still no heat? Perhaps the gas line has been shut off. It should be located within at least six feet of the furnace. If your home has more than one gas appliance, like a stove, turn the valve back on. If the flow of gas resumes, the heat you’ve been missing won’t be far behind. If nothing changes, it’s time to contact Air Professionals.

Our well-trained and experienced technicians service and repair all makes and models of gas furnaces. So, any time you have a problem, we’ll be here to lend just the right level of assistance, with your satisfaction guaranteed.