Furnace attempts to start but shuts down with E03, fan may run briefly then stop.
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: Isolate power before removing any covers. Do not operate the furnace with the combustion cover removed. Flue work must comply with gas regulations.
User checks:
- Go outside and visually inspect the flue terminal. Ensure it is not blocked by leaves, snow, plastic bags, or insect nests.
- Check that air intake and exhaust vents around the furnace are not obstructed by stored items.
- Reset the furnace and listen: if the fan does not start at all, note this for the technician.
Technician checks:
- Inspect and clear the flue path and condensate trap for obstructions.
- Check the air pressure switch tubing for splits, kinks, or water ingress; replace tubing if perished.
- Test the air pressure switch with a manometer and continuity meter to confirm switching at the correct pressure.
- Verify fan operation, speed, and wiring; replace the fan assembly if it fails to reach required speed.
Do not bypass the air pressure switch for operation; it is a critical safety device.
Repair Difficulty
Required Part
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