LED flashes code 43; furnace may short-cycle or fail to maintain flame.
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: Working on gas valves involves risk of gas leaks. Turn off gas and power before servicing. Do not attempt to adjust gas pressure without proper tools and training.
Steps:
- Inspect gas valve wiring: Ensure the two or more wires to the gas valve are firmly connected and not corroded or damaged.
- Check ground: Verify that the furnace cabinet and burner assembly are properly grounded to the electrical system.
- Observe flame behavior: Through the sight glass, watch the burners. If they drop out randomly while the inducer and blower continue, suspect gas valve or board issues.
- Power reset: Turn power off for several minutes, then restore and observe if the code recurs.
When to call a technician: Gas valve and control board diagnostics require manometers and electrical testing. A licensed technician should handle replacement and gas pressure adjustments.