I would be curious as to exactly what type of smell your having. It could be a cracked heat exchanger? You would be getting a high concentration of carbon monoxide if that's the case. This shouldn't be very hard to diagnos. I am a retired HVAC business owner and have worked on several furnaces of this type. The basic design hasn't changed for several years. They are very simple. If I was the dealer I would just replace the unit and deal with the manufacturer myself, if that's what it would take to keep the customer. Good luck