5 Reasons Your Furnace Won’t Turn On (And How To Fix It)

October 29, 2023


We don’t ask a lot from our furnaces. When it’s cold outside, keep us warm inside. Simple.

Fortunately, when your gas furnace won’t turn on, it might be simple to get the heat cranking again. There are some common reasons why your furnace won’t start. Read on for practical troubleshooting tips that may resolve your problem.

If you need professional service for your gas furnace, remember that A.J. Perri has spent more than five decades servicing HVAC systems in the New Jersey area and is just a call away.

Here’s Why Your Furnace Won’t Turn On

Typically, a heater won’t turn on for just a handful of reasons, including:

  1. Malfunctioning thermostat: This is the first thing to check. Ensure the thermostat is set to heating mode and at a temperature higher than that reflected on the thermostat. Digital thermostats can also lose programming (i.e., fail to retain temperature and time settings and reset) during power outages when backup batteries aren’t routinely changed.
  2. Tripped circuit breaker or blown fuse: Gas and propane furnaces require electricity. 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.
  3. Gas supply leaks: If you smell gas, leave the area immediately and contact your gas company for emergency services. Gas leaks can lead to explosions. When your furnace won’t provide heat, ensure your gas supply valve is open and leaks (that rotten egg smell) are not present.
  4. Pilot light problems: Older furnaces reliant on pilot lights often have issues with the ignition source. Re-lighting pilot lights can be simple, but if they frequently go out, a larger problem best addressed by an HVAC technician is likely. A professional furnace inspection should identify and correct pilot light issues.
  5. Dirty burners: Clogged burners won’t light and will burn less effectively if they do. Accumulation of dirt and grime is inevitable where burners aren’t properly maintained. A technician can inspect and clean all parts of your furnace’s burners. If your burners are clean and the furnace fails to ignite, your issue lies elsewhere.

How to Fix Your Furnace

There are several simple steps related to the issues above that can resolve your furnace troubles:

  • Check your thermostat: Make sure it’s set to heating; that the temperature setting is higher than the air temperature; and that the digital thermostat programming is intact.
  • 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. Clogged filters deprive your system of the oxygen it needs to operate efficiently.
  • Check the pilot light: Most older furnaces include pilot lighting instructions on the service panel. Modern furnaces usually won’t start without a functioning pilot.
  • Check the drain pan: A full drain pan can trigger a float switch that prevents your furnace from starting. The drain should be clear, and the pump should be functioning correctly.

When in Doubt, Ask A.J. Perri

We hope these simple troubleshooting steps will warm up your home. However, if you’re still saying, “My furnace won't turn on,” the time has come to call a professional.

Don’t hesitate to contact A.J. Perri. Our experienced technicians have been keeping New Jersey customers comfortable for more than 50 years.

Call or Book Today

Experts are standing by to help you. We’re available 7 days a week.

Last Updated: October 29, 2023