Three consecutive flame failures during one demand.

1. If boiler sparks, lights briefly and then goes out:
- Disconnect the flame sensor cable and then retry ignition.
- If the flame stays lit, allow the boiler to run for several minutes and then reattach the cable.
- If the problem persists, remove the flame sensor and inspect the burner through the sensor opening. If metal fibers are protruding from the burner, use a blunt probe to move the fibers away from the sensor.
- If the problem is still present, replace the flame sensor. 

2. If the unit locks out on flame failure during normal operation:
- Check gas pressure at the inlet to the gas valve while the boiler is operating. - Check the flame signal in the Installer Menu under Status. This will also show the total number of flame failures. If the flame signal reads less than 2.8 μA, clean the sensor and igniter. Be sure that the wiring harness is fully seated at the control.
- If the flame signal is consistently low, check the signal with the sensor disconnected. If the flame signal improves, replace the flame sensor.