Noise when furnace kicks on?

 We have a gas furnace and im not sure how else to explain this... When it goes to kick on i hear this loud noise. Sort of sounds like a metal detector would over a certain type of metal. Or maybe robotic or alien like if you ask the children here lol. It lasts for maybe 4 to 5 seconds as its kicking on then stops. Everything else sounds normal. Its working. But i don't know anything about them. I've always had electric heat. Could it be the gas line? I dont smell a leak. Please help. 

7 Answers

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  • In
    Lv 7
    3 weeks ago

    If the filter element is extremely dirty it could have collapsed and is rubbing against the squirrel cage.  If the filter is clean then maybe "elhigh" is on to something.

  • elhigh
    Lv 7
    3 weeks ago

    That sounds like a spark ignition system.

    Some furnaces ignite with a glowing hot heat element, others with a pilot flame (uncommon in modern applications) and some with a spark ignitor. The high voltage spark sometimes makes a noise you can hear.

  • John
    Lv 4
    3 weeks ago

    Fire Box heating up makes spooky noises.

  • martin
    Lv 7
    3 weeks ago

    Something in there is maybe loose, misfit, or rattling. Don't mess with it yourself. Get someone with experience.

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  • 3 weeks ago

    The rapid clicking noise you hear, when the furnace is starting up, is the spark arcing across the spark igniter .

    The spark continues until the flame sensor 'senses' flame from the burners, then the spark igniter goes dormant until next time.

    That is a normal amount of time of sparking sound for your furnace.

  • Mark
    Lv 7
    3 weeks ago

    No, the metal ducts (and furnace) are expanding with the heat.

  • Jay
    Lv 6
    3 weeks ago

    good to know i guess

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