rocketman wrote:
I have an Amana GHN90A50 furnace (circa 1987) that has an ignition
problem: I will occasionally notice the house is cold, with the temp
well below the setting on the thermostat. When I check the furnace,
the blower is running, the ignitor is glowing but no ignition. If I
then set the thermostat lower than the room temp, the blower and
ignitor shut off. I wait a few seconds (which I guess allows the
furnace to reset) and raise the temp on the thermostat. Then
everything is fine: the blower and ignitor come on and the burners
ignite.

I have a suspicion that this only happens (and then, only
occasionally) when we set the thermostat low for the night (60 or 61
degrees) but I have not tested this theory. Strangely, our tenants in
a house we rent had the same problem with a new furnace we installed
there a year ago; they set it low (maybe 55 degrees) because they were
out for a few days and found that the furnace didn't ignite.

Any suggestions?

I do not know what tools you have or what your capabilities are, but I
would hang a volt meter across the valve coil terminals to see if the
24v AC is being applied when heat was being called for. That will tell
you much about your problem.