The furnace lights but shuts off after a few seconds; the status LED shows 4 repeating flashes; it may retry ignition several times.
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: Turn off power and gas before removing the burner compartment door. Allow burners to cool.
Steps to check:
- Clean flame sensor: Locate the flame sensor rod on the burner assembly of the Luxaire furnace. Remove the mounting screw, pull out the sensor, and gently clean the metal rod with fine steel wool or emery cloth until it is shiny. Wipe it with a clean, dry cloth and reinstall it firmly.
- Check ground connections: Verify that the burner rack and gas valve have solid metal-to-metal contact with the furnace chassis. Tighten mounting screws and clean off any rust or paint that may interfere with grounding.
- Inspect burners: Look for rust, debris, or misalignment that could prevent the flame from reaching the flame sensor. Clean burner ports with a soft brush and compressed air (wear eye protection).
- Verify gas supply: Ensure the manual gas valve is fully open and that other gas appliances operate normally. Low gas pressure requires professional testing.
When to call a pro: If cleaning the flame sensor and burners does not resolve the 4-flash code, a technician should check the microamp flame signal and may need to replace the flame sensor or control board.