I have a Lennox G16 Conservator furnace that is 27 years old. Last year during maintenance service, the control unit was replaced with a Honeywell S81610u. We do not use this furnace since it controls guest room. This year, as part of maintenance, this furnace was also tested and everything was fine. Since last few days, we have started to use this furnace and intermittently the inducer motor will not stop once the furnace has turned off. Next time when the thermostat calls for heat, the furnace will not fire since the draft blower motor is running. Once I turn the furnace off/on, then everything works for a few heat cycles and again same problem.
Any suggestion on what might be the problem here?