The unit was running and lost the flame signal. This condition occurred five (5) straight times during the same call for heat.
- Check wiring harness connection at the gas valve and at the main control board.
- Inspect spark electrode and associated wiring for damage and connection.
- 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.
- 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 and clean the heat exchanger as necessary.
