Furnace runs but produces no heat; blower operates, but supply air is cool or only slightly warm.
Safety Warning
This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.
If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.
Possible Causes
How to Fix / Troubleshooting
Safety: If you smell gas, shut off the gas supply immediately and ventilate the area. Do not operate electrical switches.
Steps:
- Check thermostat mode: Ensure the thermostat is set to "HEAT" and the fan is set to "AUTO", not "ON" (which can run the blower without heat).
- Verify gas supply: Confirm the manual gas shutoff valve to the Atlantic furnace is open and that other gas appliances work.
- Observe ignition: Through the sight glass, watch for the igniter glowing and burners lighting when there is a call for heat. If the blower runs but there is no ignition sequence, the control board may be skipping heat due to a fault.
- Check for stored error codes: Many Atlantic furnaces store fault codes even if not currently displayed. Refer to the user interface or LED flash codes and then follow the corresponding repair steps.
Recommendation: If the furnace never attempts ignition but the blower runs, a professional diagnosis of the control board and safety circuits is advised.
Repair Difficulty
Required Part
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