Turned on the furnace today since our house is getting colder. First off, very little air was coming out of the vents. Then I noticed the smell of smoke and flipped on the lights to see smoke around the top of the ceiling. The whole house seemed to be filled with it. So I shut the heater off and switched to fans to dissipate the smoke. Opened windows too.
Switched back on just the fan for the A/C and no more smoke. Any ideas? A/C was serviced in the summer with a new fan motor put in. Furnace was worked on last winter.