The Display Says 55: Checking a Wine Unit With a Probe

Owners often ring to say a wine cooler’s panel reads 55 but the wine seems too warm, or too cold, or simply not right. On the island, where lake-damp air and a busy glass door both push a zone about, the display is the last place to look for an answer, because it is not measuring the wine at all.

What the number means

Take the panel at its word and no further: the temperature on it is the set point, the figure the zone has been told to hold. It is not a reading of the air in the cabinet or of the bottles. A display that says 55 means someone chose 55.

The control does measure. It reads a sensor in each zone, the zone thermistor, and compares that reading with the set point to decide when the zone needs cooling. Because the panel shows the set point, a sensor that has drifted can leave the display showing the same tidy number while the zone sits warm or cold.

Sub-Zero’s undercounter refrigeration guides add one more trap. A unit left in showroom mode shows its settings and does not cool, and the guides list it among the reasons a cabinet runs warm.

The glass-of-water check

Our own method needs nothing special. Use any thermometer that can sit in liquid, stand it in a glass of water so the bulb is covered, and put the glass in the middle of the zone, halfway back and halfway up. Leave it twelve hours before reading. The water stands in for a bottle: air changes every time the door opens, while liquid changes slowly, so what the glass reads is far closer to the bottles than any reading of the air.

On a dual-zone unit, use two glasses and two thermometers, one per zone, and read them together. Pick a night when the door will stay shut and nothing new goes in, because a freshly loaded rack lifts a zone for hours.

Reading the two numbers

Put each probe reading beside its zone’s set point. Three patterns cover most of what we see.

Close agreement. Within a few degrees, the zone is doing its job and sits inside the movement any cabinet shows in use. If the wine still seems off, the setting may simply not suit it.

A steady gap. The probe sits the same distance from the set point on a second quiet night as on the first. That points at the zone’s sensor or its connection, or at air not reaching the glass: bottles packed hard against the back wall, a blocked vent, a fan that has slowed.

A wandering gap. The difference changes from night to night, or a zone is right one morning and warm the next. Look first at the door, for anything holding it off the gasket or a seal that has lost its grip. If the door is sound, the zone’s fan or coil comes next, and finding which is wine storage repair.

After the reading

Keep both readings, the set points and the date to hand when you call. The note on what to have ready before you call lists the rest: the model and serial from the rating plate, and anything that changed lately. Two honest probe readings decide which parts cross the bridge with us far better than a description of how the wine tasted.

Before you call

1. Step 1

   Find a thermometer that can go in water

   Any thermometer that is safe to submerge will do; no special instrument is needed.

2. Step 2

   Set one glass in the middle of each zone

   Fill a glass so the bulb is covered and stand it halfway back and halfway up the zone, away from the walls and the door.

3. Step 3

   Keep the door shut for twelve hours

   Choose a quiet night with no new bottles going in. Opening up for an early look only muddies the result.

4. Step 4

   Read both, then compare with the panel

   Write each probe reading beside that zone's set point, with the date and the time you took them.

Past these checks the fault is inside the machine. Call Mercer Island Sub-Zero Service on (206) 208-3377 and say which step changed nothing.

Asked about this

Why does my Sub-Zero wine unit show the same temperature all the time?

Because it is showing the set point. The number on the control panel is the temperature the unit has been told to hold, not a live reading, so it will not move when the door opens or the zone warms. Only a thermometer standing inside the cabinet tells you what the bottles are actually at.

My probe reads four degrees above the setting. Is that a fault?

Not necessarily. A zone moves around its setting all day, pushed by the room, the humidity and how often the door opens, so one reading settles nothing. Repeat the check on a quiet night with no new bottles. If the gap comes back the same or larger, Mercer Island Sub-Zero Service, (206) 208-3377, can test that zone's sensor and airflow at the unit.