No flame detected.
GFA: Safety time expired
Check that ground lead is properly connected, replace if defective.
Check that gas cock is open.
Check inlet gas pressure; correct if needed.
Check power supply.
Check electrodes for visual damage; replace if defective.
Check flue gas system; clean or repair if defective.
Check gas/air ratio; correct if out of range.
Check gas valve; replace if defective.
In room air operation, check air supply or ventilation apertures.
Clean the condensate trap.
Remove diaphragm at fan inlet connection and check for contamination or cracks.
Check heat exchanger for soiling.
Check gas cock; replace if defective.
Insert code plug correctly; replace if defective.