The fan speed is being increased due to the flame current going below 5 microamps.
- Inspect spark electrode and associated wiring for damage and connection.
- Check for proper electrical grounding of the unit.
- Check incoming supply gas pressure. Natural gas pressures should be between 4 - 14 inches w.c. and LP gas pressures should be between 8 - 14 inches w.c.
- Verify that the plastic hose from the gas valve to the air inlet is connected and is not damaged.
- Verify that the vent/air intake pipes are correctly installed and that there are no obstructions.
- Check for 24 vac to the gas valve at the 2-pin connection on the side of the main control board during the ignition attempt. If no voltage is present, replace the main control board.
- If 24 vac is present at the main control board, check the wiring between the main control board and the gas valve. Replace the wiring if necessary. Do not disconnect the wiring from the gas valve and attempt to measure voltage at that point. The main control board can detect if the gas valve is not connected and will display the Gas Valve or Gas Valve Fail fault.
- If 24 vac is present, check the outlet of the valve to ensure the valve is flowing gas. With a manometer connected to the outlet tap of the gas valve, when the unit is in the prepurge period, there should be a negative pressure present. When the valve is energized a change in pressure should occur. If the pressure change does not occur, the gas valve is not opening. Replace the gas valve.
- Inspect flame sensor and associated wiring. Replace if necessary
- Inspect and clean the heat exchanger as necessary.
- Inspect the burner. Replace if necessary.
- Replace the main control board.
