If your relay starts to buzz, it indicates a failure for one of two reasons:
- One, your low voltage relay may have failed in either the ON or OFF position and will need to be replaced.
- Or two, you have a bad switch connected to your relay that is stuck in the ON position.
These momentary switches should energize only at the moment of contact, but when sticking they keep the coils in the relay energized, hence causing the buzzing noise.
To fix the issue, swap out a working switch connected to a different relay and wire it to the buzzing relay. If the buzzing sound stops, then replace the defective switch. If the relay continues to buzz, then it is time to replace your relay.