We have Janitrol / Goodman GMP Series gas furnace. Recently, the furnace would turn off before set temperature on the thermostat. I had a Lux programmable thermostat and thought this was the problem. I replaced the thermostat with a Honeywell programmable thermostat and it worked great. The heat turned on and off as desired for one day. Then this morning we are back to an indoor temperature reading below the desired temperature (which for us is 70) on our new thermostat. So it is not the thermostat. Last year we replaced the motor, capacitor and the venter blower assembly - so it is not these parts. It seems to be an electrical problem. Any information will be appreciated.