Oil Furnace and new Hot Water heater Fume Back up – we have had this issue for years, but no one can find problem after several tech visits. Fumes from furnace issue enter house through ducts: · No issues at all if furnace temperature kept at daytime level (comes on frequently)· If furnace turned down at night to cool house (gets colder between firings) - so furnace only comes on occasionally the issue of fumes starts – to eliminate this we simply turn off the furnace before bed and have done so for years. Turn it to daytime temperature in the morning and no problem during the day.· New Hot water heater – same fumes but is only on for a short period (15 min max) so issue is minimal but there. It smells worst at the motor. Doesn’t get pushed upstairs.· No CO2 issues· Techs have checked whatever they do and no one can find any issues at all. Anyone with any ideas I can relate to my next tech visit?

While investigating my furnace short cycle problem I found that the voltage to the flame sensor from the control board reads as 9VAC while the wiring diagram shows it should be getting line voltage (120VAC). I’m guessing this prevents the flame sensor from doing its job. Any ideas for next step? Goodman GMV90905CXA gas furnace with White/Rodgers 50V51-290 (two stage) control board. Furnace is 15 years old, control board is a newer replacement for the original. Was working fine until recently.