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trussell
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?

Re: HVAC Noise Problem
trussell wrote:

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.

trussell
Re: HVAC Noise Problem
Ravens53 wrote:

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".

trussell
Re: HVAC Noise Problem
YukYuk wrote:

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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