Dettson furnace starts inducer, but burners do not light; control board shows E2.

Safety first: Turn off power and gas before working inside the furnace. Verify no gas smell is present before proceeding.

• 1. Confirm gas supply: Make sure the manual gas shutoff valve near the furnace is fully open. Check that other gas appliances in the home operate normally.
• 2. Inspect the hot surface ignitor: Remove the burner access panel. Locate the ignitor near the burners. Look for cracks, white spots, or broken elements. Do not touch the element with bare fingers. If damaged, replace with the correct Dettson-compatible ignitor.
• 3. Clean the flame sensor: The flame sensor is a small metal rod in front of a burner. Remove the mounting screw, gently clean the rod with fine steel wool or emery cloth until shiny, then reinstall. Ensure the ceramic insulator is not cracked.
• 4. Check wiring to gas valve and ignitor: Inspect harnesses from the control board to the gas valve and ignitor for loose plugs, burnt connectors, or damaged insulation. Reseat connectors firmly.
• 5. Observe ignition sequence: Restore power and gas, then call for heat. Watch through the sight glass: inducer starts, ignitor glows, then gas should flow and burners light. If the ignitor glows but no flame appears, the gas valve or gas supply may be at fault and should be tested by a qualified technician.
• 6. Replace faulty components: If cleaning the flame sensor and confirming gas supply does not resolve E2, replace the ignitor or flame sensor as indicated by testing. Gas valve diagnosis and replacement should be left to a licensed gas technician.