Furnace burn smell
I just fired up the furnace as it's been quite cold latetly (now that I bought an air conditioner LOL) and noticed a burn smell. Before I got my AC, I rewired the thermostat so I could control the fan only, and also removed a patch in the basement so the return takes basement air. I'm suspecting the burn smell might be dust build up on the heat exchanger, but I don't recall smelling this when I turned it on for the first time in winter.
What are things I could look for to ensure all is normal? I turned it off for now, just wanted to run it for an hour or so just to bring the house above 15C anyway, it's not freezing or anything.