Got called out for no heat, go to check if stat is sending signal to furnace and find this gem:
I'm willing to bet this poor Lennox ran with the door switch taped and no filter for WEEKS while they did the drywall, sanding, etc in here. A closeup:
You can see where my finger left a clean spot on the cabinet. YIKES. I couldn't clean it right there because the customer wouldn't pay for it (new house), so we have to wait to see if builder will pay for it.