Why is my wine cooler not holding temperature?

Why we start there

On a dual-zone unit, one zone holding while the other climbs is good news: the working zone proves the compressor and sealed system are fine, and the fault belongs to that zone's own evaporator, fan or damper. On wine, two degrees is damage rather than drift, and in this valley the cabinet is frequently worth less than what is inside it, so it gets treated accordingly.

What happens next

Ambient is the first question we ask about any wine cabinet in Temecula, because these units are built to hold a narrow band against an ordinary room and a great many of them are not standing in an ordinary room. A bar off a great room, a dining room behind west-facing glass, a converted closet kept shut, a covered patio: every one of those climbs through the afternoon and only lets go after dark, and the cabinet spends the whole evening making up ground it lost between two and seven. From the outside that looks like a unit reading correctly every morning and running high every night. Nobody calls it broken until the wine says otherwise, and by then it has been happening for months.

Condensation is a separate fault from a temperature drift and gets misdiagnosed as one constantly. Cooler, damper evening air against glass that has been warm since lunch will sweat, and if the pane heater has failed, the seal has flattened or a hinge has dropped, it goes on sweating long after the room has settled. Turning the setpoint down makes it worse: colder glass condenses more, and the compressor runs longer for no gain at all. Damp along the gasket line, water pooling in the bottom of the cabinet, and a musty smell in the racks all belong to this same group of faults, and not one of them is fixed by the temperature control.

If that matches what yours is doing, say so when you call — it decides which parts come on the van.