Similar story as JeffD,

The house I live in now as built by an electrician, he and his family lived in the house for 17 years, then I (should say the Bank, DW and I) bought it. In our first winter I had the gas furnace inspected/serviced and the techniciam found the tin-foil wrapper from a cigarette pack wrapped around a blown fuse in the furnace! The heat exchanger also had a crack in it and I had to replace the entire furnace.

Along the same topic, we could often smell exhaust fumes within the house (we were blaming the new furnace) but could never find the actual source. After a couple of months I discovered that the gas water heater's plastic exhaust pipes were never glue together at the joints, only held together by friction and the fumes were leaking from there.

Two dangerous defects about 4 feet apart in a "new to me" house!

Mike