HELP..Goodman GMP 100-4, no blower in "auto"

[TLL]

*With the stat in "heat" mode & fan in "auto", furnace cycles normally until the burner lights, burns for 30 sec... No blower & shuts down. Recycles, ignitor glows but no ignition. Cleaned flame sensor, no difference.

*With stat in "heat" & fan in "on" position, everything works fine, heater runs, shuts off at set temp. (Manually turn off fan.) The flame sensor must be working with this method if burner stays lit, right?

What function is bypassed with fan in "on" that is not working with fan in "auto"?

[paul52446m]

*With the stat in "heat" mode & fan in "auto", furnace cycles normally until the burner lights, burns for 30 sec... No blower & shuts down. Recycles, ignitor glows but no ignition. Cleaned flame sensor, no difference.

*With stat in "heat" & fan in "on" position, everything works fine, heater runs, shuts off at set temp. (Manually turn off fan.) The flame sensor must be working with this method if burner stays lit, right?

What function is bypassed with fan in "on" that is not working with fan in "auto"?

haven't really heard of that one. `If it did not prove on the first try, that would be ether the flame rod or the electronic board. If you get no flame on the second try but you get glow bar. i would say it has to be a problem in your electronic board. I don't know if it run long enough for the blower to come on on the first try. Ether way i think its in the board. Later Paul

[TLL]

haven't really heard of that one. `If it did not prove on the first try, that would be ether the flame rod or the electronic board. If you get no flame on the second try but you get glow bar. i would say it has to be a problem in your electronic board. I don't know if it run long enough for the blower to come on on the first try. Ether way i think its in the board. Later Paul

Thanks Paul. Being unemployed, I was really hoping it would be something simple and cheap, but I fear you are right.