Vent, Valve & Volt
Furnace clicking but won't ignite

You can fix this

Likely cause: the furnace switch or door panel

If the furnace switch is off or its door panel isn't seated, a safety switch keeps it from starting.

Why this happens

Trane lists power among the first checks for a furnace that won't ignite. Honeywell notes that a furnace door safety switch cuts power when the panel isn't fully seated, and warns never to tape, bypass or disable it.

How to fix it

  1. Turn the furnace power switch on.
  2. Press the front door panel firmly into place so it sits flush. Don't tape or hold the door switch down.
  3. Set the thermostat to Heat and wait a couple of minutes for the furnace to start.
  4. If it starts clicking without lighting, go back and check the filter and gas handle.

If this does not fix it, tell the HVAC technician

  • Whether the switch was off or the door panel was loose.
  • Whether the furnace started once power was restored.

Build the full list: what to tell the HVAC technician.

Start this troubleshooter over

References (every fact above comes from one of these pages)
  1. Trane: Furnace not igniting
  2. Honeywell Store: Honeywell thermostat not working

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