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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.

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  • If you could get a clear recording of the sound, that might be helpful.
    – Tester101
    Commented Mar 1, 2016 at 3:03
  • Get an HVAC guy or firm. 6-years is a little long, every 5-years is when you want to have a Gas system serviced, tuned & cleaned. There's really very few, if any, user-serviceable parts & adjustments as proper testing needs to confirm continuity & parts can be contractor only restricted. The problem could be part of a chain of minor issues & not having it addressed immediately may have killed a part that could've been simply adjusted. $200 or $300 every 5-years is a real bargain for something you depend upon daily.
    – Iggy
    Commented Mar 1, 2016 at 3:06

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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!

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  • I'm not sure that a worn bearing speaks to quality of an entire brand. We use a Lennox furnace, brand-new in 2008. I've had to replace the entire draft inducer motor once - if I remember correctly, around 3 years ago. One bad component doesn't kill the entire brand IMO, in most cases...
    – alt
    Commented Mar 1, 2016 at 17:35
  • A bad bearing (prob on the inducer motor) +1.
    – Mazura
    Commented Jul 30, 2016 at 18:18
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I would remove the panels that access the blower and check the blower bearings and belt condition. Sounds as if this is happening when motor shuts off and tension on the belt is suddenly reduced.

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  • Usually the lower panel just lifts off. No tools required. Should be two handholds. Lift up and pull back.
    – ArchonOSX
    Commented Mar 1, 2016 at 18:08

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