Furnace Clicking But Not Igniting

The clicks are the gas valve opening and closing as the control board attempts ignition. Without a working ignitor (glowing element), gas can't light, and the board cycles through 3 attempts before lockout.

Watch through inspection window during ignition attempts. Should see bright orange-red glow within 15-30 seconds. If you see no glow but hear clicks and possibly smell unburned gas briefly, ignitor is the issue.

Gas valve clicks when commanded (audible solenoid action) but doesn't actually open the gas flow. Ignitor glows, you hear the click, but no flame. Often the click is louder and more pronounced than normal.

Ignitor visibly glows. You hear gas valve click. But no flame. Multimeter shows 24V at the gas valve terminals during the click — valve has power but doesn't mechanically open.

After the inducer fan starts, the pressure switch must close before ignition can begin. If it doesn't close (or chatters open and closed), you hear clicking as the control board tries to proceed. Common cause: blocked exhaust vent.

Check exterior vent pipes for snow, ice, bird nests, debris. LED code typically indicates pressure switch fault.

After 3 failed ignition attempts, the control board enters lockout. The clicking stops, but earlier clicks may have been audible. Won't try again until reset.

Furnace had been clicking, then stopped. LED diagnostic light shows lockout code. Power-cycling at breaker for 1 minute clears it temporarily.

Burners actually light briefly, but the dirty flame sensor doesn't detect it. Gas valve closes within 5-10 seconds (safety), system cycles to next attempt. The clicks are repeated ignition attempts.

Watch ignition attempts. If you see a brief flame that goes out within 10 seconds, then attempts start over, flame sensor is the issue.

Manual gas valve at the furnace is partially closed, or upstream gas issue. Gas valve opens (click) but insufficient gas flow for ignition.

Locate manual shutoff valve at the furnace gas line. Handle parallel to pipe = OPEN. Other appliances working = supply is OK to the building.