I bought four ceiling fans hampton bay huntington III model 522-861. Recently I have noticed speed of two of them has become slow. What's the problem and how could I mend in?

Thank you.

Are they remote fans?

Are you using them with wall controls or dimmers?

General ceiling fan troubleshooting and help FAQ- Ceiling Fans N More (http://www.ceiling-fans-n-more.com/ceiling-fan-general-troubleshooting-and-FAQ.php)