Goodman Model # GMC070-4b

SOURCE: Furnace runs on utility power but not on back up generator power

Using the Hz meter you can adjust the governor throttle screw to raise or lower the engine speed
to get an optimum 60-62 Hz setting. You may want to load your generator with the most
common load you will be using and then adjust the screw to give you an adjustment within the
60-62 Hz range. If you set it too high, then it means you are running the engine faster than
need be and will add to premature or serious engine damage to the internal parts. It is
mechanically governed to maintain the proper engine speed once it has the standard setting in
place. Do not attempt to adjust this governor throttle adjustment screw without the proper tools
available. You can not do it by ear! If you do not have a Hz meter or tachometer available, then
you can use a conventional electric clock with a sweep hand for seconds. If you plug the clock
into the generator, a proper engine speed would make the clock do a minute in exactly 60
seconds against any other timing device. If the clock takes longer to do a timed minute, then the
engine speed is too slow and you need to raise the engine speed; turn the governor throttle
screw clockwise. On the other hand, if your clock does a minute in less than a normal clock
minute, then you need to lower the engine speed, turn the governor throttle screw counter
clockwise. Now you should have a good setting for your generators frequency setting. It is best
to do a frequency setting before doing any voltage adjustment.
I did this today and my Goodman fired right up after two days of frustration!

SOURCE: went to bed last night with heat woke up today

Does the hot surface igniter glow? If not, it is probably cracked. If this is
a 90% furnace, it could be that yuor intake air is causing the problem.

SOURCE: woke up to no heat. furnace is doing nothing.

shut power off at SSY switch,which is on side of furnace, and wait 5 or 10 minutes and turn it back on. watch the red light and see how many times it blinks. On the inside of the lower door, is a diagnosis for the red light blinking. it is probably your flame sensor. If you can take it out, clean it with a dollar bill and reinstall it and it should work.

SOURCE: goodman furnace model # GMNT100-4B

Solid red typically means bad controller. Try unplugging the furnace, wait about 30 secs, then plug it back in. The possibility that the controller was sending voltage to the valve even when there was no flame is a bad sign. If the controller starts the furnace, watch it very closely and see what it does. If the solid light comes back on, it's time for a new board.

SOURCE: goodman furnace model # GMNT100-4B

from my experience with goodman units ,it could have been a gas supply problem there are so many protective sensors that i dont think it is the unit by the way is it electronic ignitor or pilot