Cause of AC pulsating noise and vibration in wall next to outside AC?

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Old 10-10-19, 09:16 AM
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Cause of AC pulsating noise and vibration in wall next to outside AC?

We are moving into a 22-year-old house with the original split AC. Inspection and walkthroughs did not reveal any AC problems. However, when the AC is running, were now getting a pulsating noise that is coming from inside the outside wall of a room that has the AC on the outside. The pulsating noise is not noticeable on the outside of the house where the AC is, but vibration can be felt when holding my hand on the outside wall a little above the electrical box that connects to the larger of the AC units, which is running. That location corresponds to where the noise (and vibration) occurs inside the house. Any thoughts on what could be causing this noise/vibration, corrective action, and kind of service to call (since Im not a DIYer)?
 
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Old 10-10-19, 09:35 AM
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Welcome to the forums.

Do the refrigerant lines run up the outside of the house or are they in the wall ?
 
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Old 10-10-19, 12:19 PM
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They go into the wall near the outside AC unit.
 
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Old 10-10-19, 12:53 PM
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That sounds like the lines are vibrating inside the wall.
Typically the smaller refrigerant line isn't insulted and can be touching the sheetrock.

What I have done in cases like this is to locate the area where it's vibrating..... drill a small hole and inject NON expanding spray foam.
 
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Old 10-10-19, 10:33 PM
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Thanks, Pete, for your thoughts.
 
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Old 10-25-19, 12:56 AM
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Good diagnosis by Pete, based on the following comment left by AC technician who came to house: Lineset touching drywall inside guest BR wall - pulled on lineset - noise greatly reduced.
 
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