Your refrigerator is the appliance that runs 24 hours a day, 365 days a year. It's also the one customers notice making noises first, because they hear it in the quiet of the kitchen at night. Most fridge sounds are completely normal. A few of them mean something is wrong. The hard part is telling which is which.
Here are the eight most common sounds a fridge makes, what each one means, and which ones to actually do something about.
1. A Steady Low Hum
That low, almost musical hum from the back of the fridge is the compressor running. A modern compressor cycles on and off as needed and runs anywhere from 50% to 90% of the time depending on how often you open the door, what's inside, and what the ambient temperature is.
The hum should be steady. It should not be loud enough that you notice it from the next room. If it's gotten louder recently, the most common reason is that the condenser coils at the back or underneath are clogged with dust. The compressor has to work harder when it can't shed heat efficiently, and that shows up as more noise and more electricity use.
What to do: Vacuum the coils. Unplug the fridge, pull it out, and use a coil brush or just a regular vacuum hose to clear the dust. Do this once a year and your fridge will run quieter, cooler, and last longer.
2. Clicking
Periodic clicks are normal. The defrost timer clicks every 6-12 hours when the defrost cycle kicks in or finishes. The thermostat clicks when it tells the compressor to cycle on or off. The ice maker clicks when it dumps a batch of ice. Most fridges click 8-15 times a day in total, and you usually don't notice.
Clicking becomes a problem when it's rapid or repeating. A series of clicks from the back of the fridge every 2-3 seconds usually means the compressor is trying to start and failing. The internal start relay (a small device that helps the compressor get going) is shorted or weak. It'll click, the compressor will try to spin up, fail, click off, wait, click, try again. The fridge gradually warms up because the compressor isn't running.
When to call a pro: Rapid repeated clicking is a relay or compressor failure and it needs a tech. The relay itself is inexpensive but the diagnosis matters because sometimes the compressor is the actual problem and replacing the relay won't fix it. Book a visit.
3. Buzzing
A constant low buzz at the back is the compressor running, which we covered above. A louder, more electrical-sounding buzz that wasn't there before is usually one of two things.
Water inlet valve. Modern fridges with ice makers and water dispensers have an electric valve that opens to let water in. When this valve is straining (because the supply line is closed, kinked, or the ice maker has called for water but can't get it), it buzzes loudly. The fix is usually to open the saddle valve behind the fridge, replace a kinked supply line, or change the inlet valve itself.
Compressor. A buzz that builds in volume and pitch, then drops back, can be a compressor under load. Combined with reduced cooling, this often points to low refrigerant or a failing compressor. Both are professional repair situations.
4. Knocking
This is the sound that scares customers the most, and it should. Loud knocking usually means something is hitting something else.
Evaporator fan hitting frost. Most common. The evaporator fan in the freezer pulls air across the cooling coils. If frost builds up enough to touch the fan blades, you get a rhythmic knock every revolution. This usually means the defrost system is failing (defrost heater, thermostat, or timer). Unplug the fridge for 24 hours to let everything thaw, then plug it back in. If the noise goes away for a few days then comes back, the defrost system needs repair.
Compressor mount. The compressor sits on rubber isolator mounts that absorb its vibration. If the mounts deteriorate (common after 10+ years), the compressor swings and knocks against the frame on each cycle. This sounds like a deep thunk every time the compressor cycles on or off.
When to call a pro: If a 24-hour defrost doesn't fix it, or if you hear the deep thunk on cycle changes, get a tech in. Knocking that's left alone can damage other components.
5. Hissing or Sizzling
Good news: hissing is mostly normal. It's refrigerant moving through the evaporator coils. You'll hear it more on cold cycles. You might also hear soft sizzling during the defrost cycle, when the defrost heater melts ice and water drips onto the still-warm coils.
The one exception: if you smell something faintly sweet or chemical-like at the same time you hear hissing, that could be a refrigerant leak. Modern fridges use R-600a (isobutane) which has a faint, almost ether-like smell. If you suspect this, unplug the fridge, ventilate the kitchen, and call us. Don't run the fridge with a known refrigerant leak.
When to call a pro: Only if it's accompanied by a smell or by the fridge not cooling properly. Otherwise hissing is healthy.
6. Whirring or Whining
Two fans run inside your fridge. The condenser fan at the back blows air over the coils to cool them. The evaporator fan in the freezer moves cold air through the freezer and into the fridge compartment. Both make a soft whirring sound that you don't normally notice.
A high-pitched whine, on the other hand, is usually a fan motor on its way out. Bearings wear down and start whining before they fail. You have maybe a few weeks to a few months from when you first hear it. If the whine is from the freezer side and the fridge starts having trouble keeping cool, the evaporator fan is failing.
When to call a pro: Sooner rather than later. Once a fan fully fails, the fridge stops moving cold air and food spoils fast. Replacing a fan motor is straightforward for a tech. Schedule the visit before the fan dies completely.
7. Rattling or Vibration
Rattling is almost always external. It's the fridge transferring vibration to something it's touching.
Common culprits: bottles in the door rattling against each other, the drain pan at the bottom of the fridge vibrating on its mount, the fridge sitting too close to a wall and transferring vibration into the drywall, the leveling feet not being adjusted so the fridge rocks on cycle, or the water line behind the fridge resonating with the compressor cycle.
What to do: Pull the fridge out 4-6 inches from the wall. Confirm it sits level (open the door: it should swing closed under its own weight from a half-open position). Make sure nothing in the door is loose. If you can isolate the rattle to the drain pan, tightening a couple of screws usually solves it.
8. Grinding
Grinding is the worst one on this list. It's usually metal-on-metal contact and it almost always means something serious.
Most common source: a failing ice maker. The auger motor that pushes ice out of the bin is grinding against ice that's frozen into a solid block, against a worn auger blade, or against the side of the housing. Less common but more serious: the compressor itself is grinding internally, which signals end-of-life.
When to call a pro: Now. If grinding is coming from the ice maker, you might be able to fix it by emptying the ice bin and letting it produce fresh ice. If that doesn't resolve it, or if the grinding is from the compressor area, call us. Grinding compressor noises typically mean the fridge has weeks left, not months.
Quick Reference: Which Sounds Need a Tech?
Sound summary:
- Steady hum, occasional click, soft hiss: Normal. No action needed.
- Louder than usual hum: Vacuum the coils first. If still loud, call.
- Rapid clicking from compressor area: Call. Relay or compressor.
- Loud buzz from water valve area: Check supply line. If valve, call.
- Rhythmic knocking: Try 24-hour defrost. If recurs, call.
- High-pitched whine: Fan motor going. Schedule a visit.
- Rattling: Almost always DIY. Level the fridge and check items in the door.
- Grinding: Call immediately.
Need a Diagnostic?
If you're not sure what your fridge is doing, we have a few options. You can book an in-home service call, or for $40 we offer a 15-minute virtual diagnostic over video. We'll have you point your phone at the fridge while it makes the noise and we'll usually be able to tell you what's going on without an in-person visit.
Kelly's Appliance Center has been repairing refrigerators in Sonoma, Marin, and Napa counties since 1975. Diamond Certified, factory authorized, and most repairs finish in a single visit. Call us at (707) 664-9702.
