You turn up the thermostat and the furnace clicks, pauses and clicks again. Still no heat. A furnace clicking but not igniting has made it partway through startup, but something is holding up the flame. The trouble may be inside the furnace. Before you call for service, rule out the thermostat, power switch and a few other common causes.
Why Is My Furnace Clicking But Not Igniting?
One click won’t tell you much by itself. It might be a relay, the gas valve or simply the furnace starting another attempt. Don’t worry about identifying the sound. Pay attention to what happens around it.
Does a fan come on first? Look through the furnace window if it has one. You may see the igniter glow orange. The burners might light and then shut down almost at once. Make a note of the order. That’s usually more helpful than the click itself.
A furnace making a clicking noise but no flame may have:
- An extinguished standing pilot
- A failed hot surface igniter
- A dirty flame sensor
- A blocked intake or exhaust
- A faulty pressure or limit switch
- No gas reaching the burners
- A control board, thermostat or wiring problem
Duane Blanton’s article on common furnace issues covers airflow trouble, blower problems and ordinary wear.
Make Sure the Furnace Is Being Told to Run
Sometimes, a furnace clicking but not igniting isn’t a sign of trouble with the ignition system at all. Start at the thermostat. It should be on “heat,” with the set temperature above room temperature. Raise it by 5 degrees for the test. If the display is blank, change the batteries before doing anything to the furnace.
Schedules cause their share of false alarms. A weekday program, a vacation setting or an incorrect time can keep a working system quiet. Switch to a temporary hold and listen for a response.
Power is easy to overlook. The furnace switch may be mounted nearby, and it may look no different from a switch for the basement lights. Make sure it’s on. This simple mistake sometimes explains why the furnace clicks but doesn’t turn on.
Take a quick look at the electrical panel. A tripped furnace breaker can be reset once. If it doesn’t stay set, don’t keep fighting it.
Take a Look at the Filter and Vents
Slide the filter out and judge it with your eyes, not the date written on the frame. Some filters last for months. Others get dirty much sooner. Gray pleats, a heavy layer of dust or poor airflow through the material mean it’s time for a fresh one.
A dirty filter probably isn’t responsible for one lonely click. It can, however, reduce airflow enough to overheat the furnace. Once that happens, a safety switch may shut the system down.
Now go outside and find the furnace vents. On many newer systems, they’re white plastic pipes sticking through an exterior wall. Remove leaves or snow piled around the ends. Ice sometimes forms there, too. Clear what you can reach without poking a screwdriver or anything else down the pipe.
Loose debris and filter changes are reasonable jobs for a homeowner. Anything that requires opening the burner area or putting a meter on live equipment can wait for a technician. A yearly heating maintenance visit is also a good time to deal with buildup and worn parts, preferably before winter.
Older Furnaces May Have a Pilot Light
Standing pilots are mostly found on older equipment, while newer furnaces light themselves electronically.
See a small flame through the cabinet window? Check the furnace label before doing anything with it. The correct relighting steps should be printed there. If the label is missing, don’t borrow directions from another model. If the pilot goes out again, relighting it hasn’t solved the underlying problem.
Most healthy pilot flames are blue and don’t move around much. A yellow flame — or one that keeps wavering — needs professional attention. Leave the adjustment screws where they are.
Look for the Igniter’s Orange Glow
Many newer furnaces use a hot surface igniter instead of a standing pilot. The igniter turns orange when the furnace starts. Look through the sight glass if there is one. The glow should be obvious.
No glow? The igniter is an obvious suspect, but don’t order one yet. The furnace may be refusing to power it because a pressure switch or another safety device hasn’t checked in. Furnace igniter repair starts with finding out whether the part is bad or simply isn’t receiving power.
A glowing igniter changes the picture. If the burners beside it remain dark, the ignition problem is probably elsewhere. Gas supply and controls move higher on the list.
And keep your hands off the igniter itself. The material is easy to crack. On some styles, even oil left by bare fingers can shorten the part’s life.
When the Igniter Is Actually Bad
A technician can use a meter to answer the first question: Is the igniter bad or not? If the circuit is open, use the furnace model number to find the replacement. Don’t choose by shape alone. Nearly identical igniters may run at different voltages or attach to the furnace differently.
An old part eventually wears out. No mystery there. A recently installed igniter shouldn’t die without raising questions. Before another one goes in, a technician should check the voltage, consider how often the furnace has been cycling and make sure the old part wasn’t bumped during installation.
Furnace igniter replacement only helps when testing points to the igniter. A furnace clicking but not igniting may be stopping earlier in the startup process. The furnace may never reach the point where the igniter is told to heat.
Stop resetting the furnace if the same fault comes back. A twice-tripped breaker, a pilot that won’t hold or an igniter with no power also belong on the heating repair list.
Gas and Carbon Monoxide Warnings
Smell rotten eggs? Go outside and take everyone with you. Leave the thermostat and light switches alone. Call 911 and your gas utility from outside.
You won’t smell carbon monoxide. A headache, nausea, dizziness or sudden weakness may be the only clue. The U.S. Consumer Product Safety Commission’s advice is direct: Get into fresh air immediately and call 911 if you think carbon monoxide is involved.
If the furnace still won’t ignite after these basic checks, it’s time to call a technician. A few notes can save time when the technician arrives. How many times did it click? Did the small fan run? Was there an orange glow or a blinking code? You don’t need to remove a panel to collect any of that. Those few observations give the technician more to work with than “the heat is broken,” and you can make them safely.
