Every Noise a Sub-Zero Makes, and Which Ones Mean Something

A refrigerator is not a silent appliance

It is a heat pump with a motor, two or three fans, a defrost heater and several liters of refrigerant boiling and condensing its way around a closed loop. It is going to make noise.

What makes this confusing is that a built-in unit is surrounded by cabinetry, which reflects sound back into the room instead of letting it dissipate, and that most of these kitchens are hard-surfaced — stone, glass, tile. A sound that would be unremarkable in a carpeted room becomes the thing you notice at eleven at night.

So the question is not whether your refrigerator makes noise. It is which noise, and whether that particular one belongs.

The catalog

Sound	What it is	Normal?
Low steady hum	The compressor running	Yes — unless it never stops
Gurgling, trickling, bubbling	Refrigerant moving through the evaporator	Yes
Popping, ticking, creaking	Plastic and metal expanding as temperature changes	Yes
A click every few hours	Defrost timer or ice maker starting a cycle	Yes
A whoosh or sigh when a door closes	Air pressure equalizing in a sealed cabinet	Yes
Water running, then a thud	Ice maker filling, then harvesting a batch	Yes
A hiss during defrost	The heater melting frost off the coil	Yes
Rattling	Something loose, or the unit touching cabinetry	No
A new buzz	A fan obstructed, or an electrical issue	No
Rhythmic ticking or slapping	A fan blade hitting ice or debris	No
Grinding or squealing	A motor bearing failing	No
A hum that never stops	Not a noise problem — a runtime problem	No

The rest of this guide explains the ones in the bottom half of that table, because those are the ones you came here about.

The four that mean something

Rattling

The easiest to diagnose and the most common of the four, because it is usually not the refrigerator at all.

Work outward from the unit. Is anything resting against the cabinet, the toe grille, or the panel above the doors? Is there a bottle or a jar on a shelf that vibrates in sympathy with the compressor? Is a cabinet door or a drawer front touching the refrigerator's own panel?

Then check the unit is sitting properly. A built-in that has shifted, or a leveling foot that has worked loose, lets the cabinet transmit vibration into the joinery around it — which is a very effective sounding board. A unit that is a few degrees out of level also puts its doors out of square, so a rattle plus a door that no longer seals cleanly is a single problem with two symptoms.

If none of that finds it, the rattle is inside the machine compartment, and it is either something that has fallen in there or a fan mount that has loosened.

A buzz that is new

A quiet electrical buzz that has always been there is the compressor or a transformer, and it is normal. A buzz that appeared recently is not.

The usual cause is the condenser fan. It sits behind the grille in a compartment that collects dust, and when that dust builds up around the blade the fan cannot spin freely — the motor works harder, and the sound changes from a smooth rush to a strained buzz. Cleaning the condenser fixes it, and that same cleaning prevents most of what else goes wrong with these units.

Rhythmic ticking, slapping or scraping

A sound with a regular beat that keeps time with something spinning is a fan blade striking something. Two things it usually strikes:

• Ice, if the sound comes from inside the freezer. That means frost is building where it should not be, which points at the defrost system rather than the fan.
• Debris or a bent shroud, if it comes from the machine compartment.

Neither is urgent tonight, but neither improves. A blade hitting ice will eventually crack, and a freezer building frost around its evaporator fan is on its way to not freezing at all.

Grinding or squealing

This is the one to act on. A motor bearing that has started to make noise is a bearing that has started to fail, and the failure mode is that the motor stops.

If the motor that stops is the condenser fan, the unit loses its ability to shed heat. The compressor keeps running against rising pressure, the compartments start to warm, and what began as a fan motor becomes a compressor. That is the difference between a moderate repair and one of the most expensive jobs on the price list.

If it is the evaporator fan, cold air stops circulating: the freezer may still be cold while the refrigerator warms up, which is a symptom people usually attribute to something else entirely.

The hum that never stops

This one belongs in a category of its own, because it is not really a noise complaint.

People arrive at it as a noise — the kitchen is never quiet any more, and that is what they notice. But a compressor is meant to cycle: run, reach temperature, stop, rest, start again. A healthy unit in a Miami kitchen runs a good deal of the time, especially in August, but it does stop.

A compressor that never stops is one that never reaches its target. The compartments may still be cold, which is why this goes unreported for months, but the unit is working continuously to hold a temperature it should reach easily, and every hour of that is wear it does not get back.

The causes, roughly in order of how often we find them:

1. A dirty condenser. Far and away the most common. The unit cannot shed heat, so it never catches up.
2. A door not sealing. A gasket that has hardened lets a slow stream of humid room air in, and the unit spends its life removing it.
3. A condenser fan that has stopped. Same result as a dirty condenser, arriving faster.
4. A system losing refrigerant. Less common, more serious, and usually accompanied by compartments that are genuinely not cold enough.

What to do tonight

If the sound is a rattle, spend five minutes on the easy causes. Move what is touching the cabinet, check the unit is level, take the grille off and look for anything that has fallen in.

If it is a buzz, clean the condenser. It is the answer to that sound more often than not, and it is the answer to a great deal else besides.

If it is a grind, a squeal, or a rhythmic tick, book a visit. Those are mechanical, they are cheap to fix while they are still noises, and they are expensive once the part they belong to stops.

And if it is a hum that has simply not stopped for days — that is not a sound to fix. That is a unit telling you it cannot keep up, and it is worth finding out why before it stops keeping up altogether.

What to say when you call

Sound is genuinely hard to describe over the phone, so bring these three answers instead:

• When did it start, and did anything change around then
• Is it constant, or does it come and go with the compressor
• Which end of the unit does it come from — the top grille, the interior, or underneath

Those three narrow it down more than any adjective will, and they are the difference between a visit that finds it in ten minutes and a visit that spends an hour looking.