pete_c
Guru
signal15,
Where are the supply and return vents / ducts in the room. You mention removing drywall in the ceiling? Do they come from below or above? How does the fan get its power? If you could shut on / off the power supply and maybe use a stethoscope / glass/plastic cup you might be able to hear hum from a relay or motor.
Where are the supply and return vents / ducts in the room. You mention removing drywall in the ceiling? Do they come from below or above? How does the fan get its power? If you could shut on / off the power supply and maybe use a stethoscope / glass/plastic cup you might be able to hear hum from a relay or motor.