I have a couple of 20 year old forced air furnaces - the air handler/blower on each was identified after 6 months or so, though there is still some conflation between the two. Long story here:
Both furnaces plug into 120V dedicated outlets (meets code here), so I have since hooked both to HS110 smartplugs. That illuminated the additional components of the furnace heating cycle beyond just the main blower.