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  1. #1
    Join Date
    Jul 2008
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    3

    Default HVAC Noise Problem

    From time to time, just before the HVAC system starts up, there will be a transformer or electrical buzzing noise, which occurs for approximately 3 to 5 seconds followed by a loud thumping sound. What exactly is happening and how do I fix it?
    Last edited by trussell; 07-20-2008 at 03:07 AM. Reason: grammer error

  2. #2
    Join Date
    Jan 2008
    Location
    Lakeland ,MN
    Posts
    356

    Default Re: HVAC Noise Problem

    Quote Originally Posted by trussell View Post
    From time to time, just before the HVAC system starts up, there will be a transformer or electrical buzzing noise, which occurs for approximately 3 to 5 seconds followed by a loud thumping sound. What exactly is happening and how do I fix it?
    It could be the compressor on the outside unit needs a charge. Causing a hard start condition. I have also seen the contactor chatter because the electrical coil and contactor springs are weak. The contact points are pitted and also may chatter when being closed by the electrical coil. Not all units have what I described above but it could be the problem.
    Harry

  3. #3
    Join Date
    Jul 2008
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    3

    Default Re: HVAC Noise Problem

    Quote Originally Posted by Ravens53 View Post
    It could be the compressor on the outside unit needs a charge. Causing a hard start condition. I have also seen the contactor chatter because the electrical coil and contactor springs are weak. The contact points are pitted and also may chatter when being closed by the electrical coil. Not all units have what I described above but it could be the problem.
    "Thanks for the advice".

  4. #4
    Join Date
    Jul 2008
    Posts
    3

    Default Re: HVAC Noise Problem

    Quote Originally Posted by YukYuk View Post
    Free standing window or through the wall unit or central A/C? or

    "Central A/C"

    Where is the noise coming from? Inside your air handler or outdoors?

    "The noise is coming from inside the main unit in my utility room"

    Indoors: Indoor fan have a belt? Dislodged or clogged air filter? Any other obstruction for return air intake (broken/closed damper? dirty ducts?) Something preventing the air handler's fan from rotating freely on start-up?

    "No fan belt, the air filter is neither dislodged or clogged"

    Otherwise possibly the motor post is bent, bad bearing, needing either to be lubricated, bent blade or dirt collections on the edge, dirty or bad brushes, bad contacts, or a bad start-up capacitor perhaps. Something inside the unit outdoors obstructing the fan maybe. Another possibility is that some where in the circuit you have a bad contact or resistance, sticky relay, etc. - even a bad signal/contact from the thermostat another place to clean and trouble shoot from and through to the system.

    When was the last time you did or had full maintenance cleaning of both your air handler and outdoors?

    Time to whip out your owners manuals for maintenance and trouble shooting instructions or call a pro.
    "The last time I called a PRO, the system wouldn't produce the problem. It is not very consistant and doesn't happen all the time".

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