Why Do Relays Sometimes Chatters When Coil Voltage Drops?

Automation & Controls
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1

I noticed that sometimes the relay keeps making a chattering sound, like ON-OFF rapidly.
Is this because of low voltage or something else?

2

Yes, relay chatter almost always means low or unstable coil voltage.
If the coil doesn’t get enough voltage, it cannot hold properly and keeps dropping out.
This can be caused by:

  • Loose terminals

  • Undersized wiring

  • Long cable length causing voltage drop

  • Weak power supply or control transformer

Fix the voltage issue and the chatter usually stops right away.