It runs fine for the approximately 15 minute heat cycle. It appears as though it happens as the thermostat is satisfied and the gas valve shuts off. The vibration is heard upstairs and throughout the house. The furnace runs after the vibration for a couple minutes. There is no obvious location when at the furnace. Should I remove the lower panels to be closer to the apparent noise (with buttons pushed to keep the unit operating?).Thermostat wiring issue – gas valve solenoid chatter?
The furnace is a 90% Arcoair 6 yrs. old and this is the second year with this issue. I originally thought it was a shorted sump pump electrical issue as it sounded originally like an arcing when the sump pump came on (from upstairs). New sump pump and continued noise and further investigating proves otherwise.
Best Answer
I agree with @nomind as far as removing the panel on the furnace and inspecting the the blower.
However, I am thinking the fan reaches a particular speed and the balance of it hits a resonant frequency as it slows back down through that speed.
I would suspect lint has built up on the fan and is affecting the balance of it. Remove the inspection panel and clean the fan thoroughly with a vacuum. If the vibration continues after that I would suspect a worn bearing but after only 6 years of use that would not speak very well of your brand of furnace.
Good luck!