Softener emits a persistent humming noise even when not regenerating

Safety first: Unplug the unit before touching electrical components. Only qualified persons should perform live electrical tests.

Step-by-step checks:

• 1. Localize the noise: Listen closely to determine whether the hum is coming from the Marlo transformer, drive motor, or control board.
• 2. Inspect mounting: Ensure the transformer and motor are firmly mounted and not vibrating against the cabinet or wall.
• 3. Check for stuck relay: If the motor hums but does not turn, a relay may be stuck partially energized. This requires board inspection.

When to replace parts: Replace the Marlo low-voltage transformer if it is the noise source. Replace the drive motor if it hums without turning. Persistent relay noise usually requires a new Marlo control board.