Combustion Fan Speed Low – The boiler will lock out if it senses that the fan speed is less than 70% of expected rate for more than 60 seconds.
- Check the combustion air fan wiring.
- Check the quality of the 24 VAC signal by measuring from any connected safety to ground. A low voltage situation may cause a “false” error code
- Replace the combustion air fan.
- Replace the control board.
