I have a Carrier furnace, medel #58mvb installed 3 years ago. I have had numerous problems including Carrier replacing the unit at no cost to me. When I started to use the furnace this season there is a strong smell in the exhaust. Not inside, only outside. The tech has spent a couple of hours working on the unit and says everything checks out, but that he will call the factory. That was 6 weeks ago, no word. Can you help?

Thanks, bill