E6 code, furnace cycles on and off frequently, may not reach set temperature

Critical safety warning: A rollout or auxiliary limit fault can indicate dangerous combustion problems or a cracked heat exchanger. Turn OFF gas and power immediately. Do not operate the furnace until inspected.

• Step 1 – Visual inspection: With power and gas off, remove burner access panel. Look for signs of soot, scorch marks, or melted wiring near the burners and rollout switches.
• Step 2 – Check rollout switches: Locate the small manual-reset rollout switches near the burner openings. If a red reset button is present, press it gently once. If it clicks, it was tripped. Do not repeatedly reset without finding the cause.
• Step 3 – Inspect venting: Check the flue pipe and vent cap for blockages or disconnections. For condensing Ducane models, inspect condensate drain for clogs that could flood the secondary heat exchanger.
• Step 4 – Do NOT bypass safety switches: Never jumper or bypass rollout or limit switches. This is extremely dangerous.
• Step 5 – Call a professional: A licensed HVAC technician must inspect the heat exchanger, combustion, and venting system. Operation should not resume until the underlying issue is corrected.