I have a 1991 Goodman furnace. I used to have a problem where if I set my fan to come on automatically, the furnace will light for one minute, and then go out, without the blower coming on. If I turn the furnace on, and set the fan to always run, then it will work fine. I thought the problem may be a bad flame sensor, but I replaced it and it still does the same thing.

I told my Dad, and he came over and re-wired the thermostat. After the thermostat was re-wired, the furnace has been blowing cold air. The fan is turning on right away, but the furnace is not lighting. I noticed that since the thermostat was re-wired, that the fan comes on immediately, when before there would be a delay between the furnace lighting and the fan blowing. The sensors that require that the flame is lit before activating the fan seem to have been bypassed or are not working. After the fan is turned on, the furnace does not attempt to light.

Before the re-wiring setting the fan to automatic, would cause the fan not to come on. Now it comes on if the thermostat picks up that the temperature is below what it should be, but the furnace is not lighting.

Does anyone know what need to be done to get this furnace up and running?