This afternoon, I investigated a noise issue with a Carrier central air conditioning system at a home in Denton, Texas. The homeowner reported an unusual rattling sound coming from the outdoor condenser unit. Upon inspection, I found that one of the condenser fan blades had become loose, causing it to vibrate against the fan housing. I carefully tightened the blade attachment and rebalanced the fan assembly. I also performed a general cleaning of the condenser coils and checked all electrical connections. The system is now operating quietly and efficiently, meeting the homeowner's expectations.