Found this one a couple of months ago. I love doing contract work for another oil company and getting to go where no one has been or dared to venture in ages. Call was for an oil fumes smell in the house. Customer said they had noticed the smell for the past week. A week? More like years if you ask me.
The pre-fab chimney was missing its cap so the rain caused the smoke pipe to rust out at the elbow. The duct directly under the rusted out smoke pipe is the RETURN air duct which had a huge hole rusted through it. Oh, and it was running when I arrived. I killed the power real fast and went in search of my camera.
I showed the homeowner and her son the photos I'd taken, explained what was going on and informed them that someone would be out the next day to give them a quote on a chimney, fix the duct work etc. Oh and you might want to invest in a space heater or two because I'm leaving this thing turned off. I get to listen to the old "it's been heating real good, I just don't like that oil smell." Yes, and you're lucky you did not either die of CO poisoning or set your house on fire. I love how one homeowner will be worried to death over something dumb like a humming relay and another will act as though having almost set their house on fire or worse is no big deal.
Glad I gave the big boss a heads up and showed him what I'd run in to since the customer called their oil dealer the next day to say that all I'd done was go under their house for a few minutes, cut their heat off and leave without telling them a thing. Isn't this work fun?