Contactor Chattering or Buzzing

Contactor making noise: causes and remedies for AC coil hum and chatter.

Symptom: Contactor buzzes or chatters

1. 1

   Check coil voltage

   Measure voltage at coil terminals. Low voltage (<0.85 Un) causes incomplete pull-in and chatter.

2. 2

   Dirty contacts

   Carbon build-up on pole faces. Clean with contact cleaner. Replace if pitted or welded.

3. 3

   Mechanical obstruction

   Foreign material or deformed armature. Inspect for debris. Replace contactor if damaged.

4. 4

   Coil damage

   Partial short in coil causes hum. Measure coil resistance; compare to datasheet. Replace if out of spec.