HVAC Troubleshooting

Follow our interactive troubleshooting guide to find answers to your system’s problems.
Choose from a selection of common HVAC issues or pick your product for help with fixes you can try yourself.

Why Is My Furnace Not Igniting?

Is your furnace clicking but not igniting? If your furnace does not ignite and your house is getting cold, it’s time to do some investigating.

Cause #1: Thermostat issue

This may sound silly, but make sure the thermostat is set to HEAT and the set temperature is higher than the indoor temperature. If you live with others, someone may have adjusted the thermostat without you knowing it.

Cause #2: Tripped circuit breaker/no power to furnace

Next, make sure there is power to the furnace. While the furnace burns gas or propane to heat your home, it still needs electricity to operate the blower fan, blower motor, electronic ignition system, control board, and more. Check for an electric switch near the furnace (it can look like a light switch) and make sure it’s in the ON position.

Next, check the circuit breaker box to ensure the circuit breaker hasn’t tripped. If it has, don’t reset it. It most likely tripped because there’s a problem with the furnace itself. Call an HVAC professional to find the issue and fix it.

Schedule furnace repair

Cause #2: Dirty Air Filter

A dirty furnace filter can cause a lot of problems, including failure to ignite. Check the filter and change it if it’s dirty. You should change the HVAC filter every 1-3 months, depending on the quality of the filter.

Learn more about furnace filters and when to change them.

Cause #4: Gas line issue

While uncommon, it’s possible that the gas supply to your furnace got shut off. You can usually find the gas valve shutoff within a few feet of your furnace. It’s typically located on a black or copper pipe that leads to your furnace and has a knob or lever. Check that it’s in the ON position. When in doubt, contact an HVAC professional.

Cause #5: Furnace ignitor issue

Furnaces manufactured since 2010 have an electronic furnace ignitor, which is more efficient than the old standing pilot light furnaces. If your furnace is not igniting, it could be because the furnace ignitor is not working. This is another issue that an HVAC professional can troubleshoot and perform furnace ignitor replacement if needed.

Schedule furnace repair

Cause #6: Flame sensor issue

A flame sensor is a safety device that detects a flame. If no flame is detected, it signals the control board to turn off the gas supply, preventing a gas buildup. A dirty or faulty flame sensor could cause your furnace to not ignite. You should not attempt to clean or replace the flame sensor yourself. Leave that to the HVAC professionals.

Schedule furnace repair

Cause #7: Furnace pilot light went out

Most furnaces today have an electronic ignition system. But if your furnace was built before 2010, it may have a standing pilot light. A standing pilot light provides a constant flame that instantly ignites the gas coming into the furnace whenever the thermostat signals the need for heat.

If your pilot light went out, you’ll need to relight it, using a long lighter or a matchstick. Learn how to check the pilot light on a furnace and how to relight it safely.

Cause #8: Dirty burners

If the furnace is not igniting the burners, it may be because they are dirty. We do not recommend opening up your furnace and trying to clean them yourself. If your furnace is under warranty, this type of DIY work could void the warranty. Call your HVAC company to check out the situation and perform maintenance or repair safely.

Schedule furnace repair

Prevent problems with furnace maintenance

You can help keep your home warm and cozy in the coldest of temperatures by scheduling a yearly furnace tune-up. During this maintenance visit, the HVAC technician will check the ignitor, the burners, the control board, and other parts to ensure everything is in working order. They’ll clean the burners and lubricate moving parts.

You might consider signing up for an HVAC maintenance plan, which can save you time and money. These plans usually include a maintenance visit in the spring before cooling season, and another in the fall before heating season. Some plans offer priority service and discounts on parts.

Schedule furnace maintenance

Should you repair or replace your furnace?

It depends. If your furnace is older with a standing pilot light, you could save money on your heating bills by upgrading to a high-efficiency furnace. If you’re having problems more frequently and paying more for furnace repairs, you may want to read our blog on the top warning signs it’s time for furnace replacement so you can start planning for the future.

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By Anne Fonda

A Content Writer with Trane Technologies, Anne Fonda researches topics and writes for Trane® and associated residential HVAC brands. She works in collaboration with Trane Technologies subject matter experts, offering easy-to-understand, informative content on complex topics. Her goal is to help consumers make informed decisions on the products and services they need.

She has written for HVAC and other service provider websites for over 16 years. Before transitioning to web content writing, Anne had a 14-year stint as an award-winning journalist. She graduated cum laude from the University of Missouri-Columbia School of Journalism. When she’s not working, Anne enjoys playing word games, reading, gardening, spending time with family, and visiting gardens and museums.

Expert review by Kimberly Sexton, Senior Systems Engineer