Fridge not getting cold

What it usually means

A fridge that is not cold is either not trying or trying and failing, and the difference is audible. Put your hand on the side or the back, low down and to the rear where the compressor is, and listen. A low hum with faint warmth means the appliance is running and something else is wrong. Complete silence over several minutes, with the interior light and display working normally, is the more hopeful finding, because the commonest cause of that is not a fault at all.

The cause is shop mode. Every showroom needs appliances that light up without running a compressor for a year, so manufacturers build a display setting in, and the button sequence that enables it is short enough to be triggered at home by accident or by a child. The result is exactly the symptom: full display, working light, no cooling ever. It is worth knowing that this is not always cleared by unplugging — on some appliances the setting survives a power cut, and it has to be switched off with the same sequence that switched it on. Check the manual for your model before spending anything, because there is no cheaper repair than this one.

If both compartments are warm and the compressor is running constantly, look at the outside of the appliance before the inside. A fridge cools by moving heat into the room, and it does that through a condenser — either a black grille on the back or a coil behind a vent underneath. A layer of dust, a cupboard built tight around it, or a cabinet pushed hard against a wall all reduce how much heat it can shed, and the appliance responds by running longer and longer for less and less effect. Manufacturers publish a required clearance; almost nobody leaves it.

The most diagnostic pattern of all is a freezer that is fine and a fridge that is not. Frost-free appliances have one cooling surface, in the freezer, and cool the fridge above by blowing cold air up a duct through a flap. If the fan that moves that air stops, or the duct ices up, the freezer stays perfectly cold while the fridge climbs to room temperature — so this pattern points at a fan, a flap or a blockage rather than at the expensive sealed system. A single-fan appliance also tells you something by going quiet: on many models you can hear the fan change note when you open the fridge door.

Two ordinary explanations account for a lot of the rest. Cold air has to circulate, so packing shelves solid against the rear vents starves the front of the cabinet, and a big shop takes a day to come down to temperature rather than an hour. And a fridge in an unheated garage or outbuilding fails in winter for a reason that surprises everybody: the part that decides whether to run is inside the fridge compartment, so when the room is near freezing the appliance thinks it is already cold enough and stops running, which leaves the freezer to thaw.