Why is my wine cooler not holding temperature?

What is actually going on

Wine columns and undercounter cabinets fail quietly, and a display will sit on a perfect number for months while the collection behind it runs several degrees warm, because the control is reading a spot where air moves freely and the racks are not in that spot. On a dual-zone unit the fastest diagnosis is the comparison: if one zone holds and the other drifts, the compressor and the sealed system are proven healthy and the fault lives in the drifting zone's own evaporator, fan or damper. If both zones drift together, the problem is upstream and it usually starts at the condenser.

What we check, and in what order

We leave a probe between bottles on a middle shelf and let it settle rather than taking a spot reading, because the number that matters to the wine is the one it holds all day, not the one on the display at the moment the door opened. On storage this is the difference between a fault and a tolerance. A couple of degrees is a rounding error on a refrigerator and a real problem on a collection that has been laid down for years.

Undercounter wine cabinets are the units we see fail most in San Diego, and it is about where they get installed. They go into a bar run or an island with cabinetry tight on both sides and a grille that has a few inches of air to work with, and in coastal homes that grille has been drawing marine air across an aluminum condenser for years. Corroded fins plus a restricted airflow path is the standard picture near the water, and it presents as a cabinet that holds temperature in the morning and gives up by late afternoon.

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