![](http://blog.us-kon.com.tr/wp-content/uploads/2020/09/EN_UsefulTips_Buzzing.jpg)
Excessive AC hum, buzzing, or chattering may be caused by several factors. These include low voltage supply, foreign matter/ debris on the plunger or plugnut face, worn plunger and/or plugnut face, damaged/broken spring, system pressure above that which the valve is rated for.