I have a Goodman furnace from 2000 has been running great until recently it does not seem to cinc with thermostat. when you shut unit down and turn back on it will go through all motions of starting except igniter will not glow. once you shut off and on about 7 times it will then fire up and run but will then shut off once desired temp is hit but will not turn on again, there is also no codes showing. I'm thinking it may be with the thermostat relay switch??