A dishwasher humming but not washing usually points to the wash motor, so three questions guide the checks: is something jamming it, does it have enough water, and are its start circuit and windings healthy? Telling the technician which part of the cycle hums, and whether you've found glass, seeds or labels in the filter, narrows it down quickly.
Before the visit
- •Model and serial number, from the label on the door edge or tub frame.
- •When it hums. At the start of the wash, during the whole cycle, or only during the drain.
- •What you don't hear. The swish of water spraying is the sound that should accompany the wash.
- •Anything broken, such as a glass, or labels and seeds you've seen in the filter.
- •Error codes or flashing lights.
- •Access to the kitchen and the dishwasher's lower front panel.
Safe pre-checks:
- Turn the dishwasher off, remove the bottom rack and clean the filter and the area around it. Wear gloves if anything broke. Samsung's noise guide points out that a low hum or buzz is normal, but that a loud one can mean something is caught in the drain pump impeller below the filter, and it suggests cleaning the filter and the pump opening beneath it.
- Check that the spray arms turn freely by hand.
- Run a short cycle and listen for water entering and spraying.
The checks, in the usual order
| Step | What's tested | What it rules in or out |
|---|---|---|
| 1 | Which phase hums: fill, wash or drain | A hum during drain points to the drain pump, not the wash motor |
| 2 | Filter, sump and pump inlet for debris | A trapped object can stall the impeller |
| 3 | Water level in the sump | Too little water can leave the pump unable to spray |
| 4 | The wash motor's start capacitor, on models with one, after it's discharged | A failed capacitor can make the motor hum without starting |
| 5 | Wash motor winding resistance | Out-of-range windings point to the motor itself |
| 6 | Whether the motor turns freely | A seized motor hums but can't turn |
| 7 | Door switch and control output | Checked when the motor tests good but doesn't get the right power |
Whirlpool's service manual for its 18- and 24-inch ADA built-in dishwashers addresses this symptom directly. It says a faulty capacitor may cause the motor to hum, not start, or start slowly, and its procedure has the technician discharge the capacitor, disconnect it and measure it, then check the wash pump's windings, replace a seized motor, and look for debris and a door switch problem.
Tools you may see
- •Multimeter, often with a capacitance setting, used with power off and the capacitor discharged first.
- •Service mode, to run the wash pump on its own and listen to it start.
- •Flashlight and gloves, for the filter, sump and pump inlet, where glass and hard debris collect.
Questions you'll probably be asked
- •Does the hum come during the wash or the drain?
- •Do you hear any water spraying at all?
- •Has anything broken inside recently?
- •When was the filter last cleaned?
- •Did it hum and then start on its own at some point, or never start?
- •Have you seen a code, or noticed a burning smell?
What the findings usually mean
- •Debris in the sump or pump: the motor was being held still; the pump is then checked for damage.
- •Low water in the sump: the fill side needs checking before the motor is blamed.
- •Capacitor out of range: on models that use one, this alone can explain a hum with no start.
- •Windings out of range, or a motor that won't turn: the wash motor has failed.
- •Motor and capacitor test good: the door switch or control is next.
A dishwasher that stops partway through rather than humming is covered in what a technician checks when a dishwasher stops mid-cycle.
Sources
- •Samsung Dishwasher Is Too Noisy, Samsung
- •Service Manual, Whirlpool 18" and 24" ADA Built-In Dishwashers (W11187658), Whirlpool
Good to know: A quiet hum on its own can be normal; a hum with no sound of spraying is the combination to report, and it's sensible to switch the dishwasher off rather than let it keep trying.
To have a humming dishwasher checked, call TrueFix San Antonio at (210) 401-3007 or visit our dishwasher repair page.