Goodman warm air gas furnace. Gas burner would not light.Status code light blinked continuously. Igniter glows red hot. I cleaned flame sensor with fine grade sand paper. Checked transformer line voltage 110 volts in and 26 volts out. Sufficient power to open the gas valve. Gas burner still did not light. I have not checked air filter but I will replace it anyway. Any ideas you may have concerning my dilemma will be greatly appreciated.