What this usually means
A new sound is more useful diagnostically when you note where it comes from and whether it occurs at startup, throughout operation or at shutdown.
Do not reach into equipment or remove panels. Severe metal-on-metal sound, smoke or electrical odor is a reason to turn the system off.
What you can safely check
- Indoor or outdoor source
- Startup, run or shutdown timing
- Visible loose debris outside the unit
- Any accompanying odor or performance change
When to call a professional
Schedule diagnosis for persistent new noise; stop the system and call urgently for grinding, scraping, smoke, sparking or repeated electrical buzzing.
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