Heating, Air Conditioning, Fridge, HVAC/Central Air conditioning



My family and I just moved into a brand new home here in North Carolina about 2 months ago. It contains a Carrier brand central AC system (4 ton).  As with most homes, the compressor unit sits on the ground outside the home. Our system appears to be cooling properly.  My question is about a noise coming from the compressor unit as soon as it shuts off.  Surrounding units from the neighbors do not make this noise.  The noise sounds like a "clatter" or "grinding" and lasts 1-2 seconds as the unit shuts off.  (You may compare it to your cars' valves clattering when you use a lower octane gas).

Can you tell me what is causing this noise and is it going to damage or shorten the life of the compressor?


Sorry for the delay, for some reason this service is not sending me emails I have questions...

It is normal for systems to make noise when they shut off.  The pressures in the system equalizes.  You are hearing the sound of the refrigerant equalizing.  Some in fact, make more noise or different noises then others.


Heating, Air Conditioning, Fridge, HVAC

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Craig HVAC Expert


I have been in the HVAC field for the past 18 years. I can help with most HVAC questions. I work on commerical buildings for the most part, and have yet to find anything I could not troubleshoot and repair, when repairable. I work on small 1 ton units to a 2500 ton chiller. Troubleshoot air flow, elect, and control problems. I attend regular classes to keep up with the latest and greatest.


I work on commerical sites, hospitals, gov't buildings. I can troubleshoot just about anything in the HVAC business.

5 years trade school, VFD training classes, Liebert factory training, some York and Trane factory training.

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