Furnace shuts down during operation, control shows E05, blower may continue to run.

Safety: Turn off power before removing panels. Components may be hot; allow time to cool.

Steps:

• Check air filter: Locate the return air filter near the Atlantic furnace. If it is dirty or clogged, replace it with the correct size and airflow rating.
• Inspect supply and return vents: Ensure that supply registers and return grilles throughout the home are open and not blocked by furniture, rugs, or debris.
• Verify blower operation: Set the thermostat fan to "ON". If the blower does not run, the blower motor, capacitor, or control board fan relay may be faulty.
• Locate high limit switch: The high limit is usually mounted on the heat exchanger panel inside the furnace. Check that its wiring is secure and not burnt.
• Reset and test: Some Atlantic models use manual-reset rollout or limit switches. If a manual reset button is present, press it once after the furnace has cooled. If the switch trips again, do not continue resetting; find and correct the root cause.

Warning: Repeated high-limit trips indicate overheating, which can damage the heat exchanger. If airflow is good and the problem persists, contact a professional.