I have a Payne Furnace, model 394GAW036050 that won't light automatically. Gas furnace. The first issue was that the electrode sparker would spark continuously for many minutes until the pilot flame would ignite. I switched out the pilot burner and now have a new problem. When the thermostat calls for heat, the furnace does nothing. The sparker does not spark. If a light it by hand the pilot will light and the sparker will start sparking like crazy. Once I light the furnace by hand it operates perfectly. Why won't the sparker start sparking itself when asked to? Why is gas flowing without the sparker sparking? Also, this is intermittent, sometimes it will light itself and sometimes it won't. Please help.