The Short Answer
Appliances are quiet by design, so a sound that was not there before is a diagnostic clue. Buzzing and humming usually come from fans and compressors; grinding and screeching from a dry bearing; knocking and rattling from something loose or from a fan hitting ice. The value of catching it early is that a worn fan is a small part, while the failure it leads to, an overheated compressor or a seized motor, is not.
Most Common Causes
- Worn fan bearing. Evaporator or condenser fan grinding or squealing as the bearing dries out.
- Fan striking ice. A rhythmic knock when frost builds into the fan path.
- Straining compressor. A louder hum as dirty coils force it to work harder.
- Loose mount or panel. A rattle that comes and goes with the compressor cycle.
- Dishwasher pump debris. A grinding drain pump with something caught in the impeller.
Notes by Brand
On Sub-Zero and True Residential refrigeration, a knock that appears when cooling starts is often a fan blade hitting frost, which points back to a defrost fault. On Wolf and Viking cooking equipment, a noisy convection fan bearing is the usual culprit behind a whine from the oven. On Cove, Miele, and Bosch dishwashers, a grinding drain pump usually has glass or grit caught in it. On Liebherr and Thermador units, a compressor hum that grew over time tracks back to condenser airflow.
Symptom Reference
| What You Hear | Likely Cause | Fix |
|---|---|---|
| Grinding or squealing | Dry fan or motor bearing | Replace fan motor or bearing |
| Rhythmic knocking | Fan blade striking ice | Clear frost, repair defrost fault |
| Loud hum | Straining compressor, dirty coils | Clean condenser, test compressor draw |
| Rattle with the cycle | Loose mount or panel | Re-seat and secure the loose part |
| Grinding in a dishwasher | Debris in the drain pump | Clear impeller, replace pump if scored |
Hearing a New Noise?
Book a diagnosis. Diagnostic and travel fees, if applicable, are confirmed before the appointment and before repair approval.