Furnace cycles on and off rapidly at the thermostat (clicking) but burners do not stay lit.

Safety First: Turn off power before moving thermostat wires.

• Check thermostat settings: Ensure the thermostat is configured for gas furnace (not heat pump) and cycle rate is appropriate.
• Tighten connections: Inspect and tighten all low-voltage connections at the thermostat and furnace control board.
• Bypass thermostat test: Temporarily jumper R to W at the furnace. If the furnace runs normally, replace the thermostat.
• Inspect cable: Look for staples or nails through the thermostat cable causing shorts.