A dishwasher is designed to save you time, water, and effort in cleaning dishes. When it’s functioning correctly, you load the dishes, add detergent, press the start button, and walk away knowing that the machine will take care of the rest. However, if you hear a humming noise and the dishwasher isn’t washing, this is a sign that something is wrong. Two common causes are a stuck motor or a blocked circulation pump. Understanding these problems can help you decide whether you can attempt minor troubleshooting or if you need professional assistance.
1. Why the Dishwasher Hums but Doesn’t Wash
A dishwasher’s internal washing process relies on water being sprayed at high pressure through rotating spray arms. The circulation pump is responsible for pushing the water through, and the motor powers this process. When something prevents the motor or pump from functioning properly, you might still hear a humming or buzzing sound — the sound of the motor attempting to work — but no actual washing takes place.2. Stuck Motor
A stuck motor can be caused by several issues:- Debris lodged in the motor assembly – Small pieces of broken glass, food particles, or other debris can jam the impeller connected to the motor, preventing it from turning.
- Worn bearings – Over time, the motor bearings can wear out, making it difficult for the motor to start spinning.
- Electrical problems – Faulty wiring or a failing motor capacitor can prevent the motor from starting properly.
- A humming noise as the dishwasher attempts to run the wash cycle.
- No movement of the spray arms.
- The wash cycle timing out or stopping prematurely.
3. Blocked Circulation Pump
The circulation pump is the heart of the dishwasher’s washing system. It draws water from the tub, pushes it through the spray arms, and ensures that all dishes get cleaned evenly. Common reasons for blockages include:- Food debris buildup – Even with pre-rinsing, small food particles can accumulate inside the pump housing.
- Foreign objects – Bits of glass, bones, or plastic can get lodged in the pump.
- Scale deposits – In areas with hard water, mineral buildup can clog the pump’s components.
- The dishwasher fills with water but does not spray.
- Humming or buzzing sounds as the motor struggles.
- Dirty dishes at the end of the cycle.
4. Troubleshooting Steps
If you are comfortable working with appliances, there are a few basic checks you can do before calling a repair technician:- Disconnect the power – Safety first. Always unplug the dishwasher or switch off the circuit breaker before attempting any inspection.
- Check the spray arms – Remove them and clean any clogged holes that may prevent water flow.
- Inspect the filter – A clogged filter can restrict water flow to the pump. Clean it thoroughly.
- Listen for motor startup – If the motor hums but doesn’t spin, it may be stuck or failing.
- Look for visible obstructions – Shine a flashlight into the sump area to check for debris that might be blocking the pump impeller.
5. When to Call a Professional
While minor cleaning and inspection can be done at home, diagnosing and repairing a stuck motor or blocked circulation pump often involves:- Removing the dishwasher from under the counter.
- Disassembling the pump and motor assembly.
- Testing electrical components with a multimeter.
6. Preventing Future Problems
Regular maintenance can extend your dishwasher’s lifespan and prevent issues like humming without washing:- Scrape, don’t rinse – Remove large food particles before loading.
- Clean the filter weekly – This keeps debris from reaching the pump.
- Run a cleaning cycle monthly – Use dishwasher cleaner or a vinegar rinse to remove scale and grease.
- Check for small items – Avoid washing anything that could break apart and clog the pump.