What is the loud humming or rattling from my refrigerator?

What is actually going on

Short cycling on a built-in usually traces back to a condenser that cannot shed heat, a start relay or overload on its way out, or a control being told a temperature that is not real. Steady noise is more ordinary: a rattle or buzz behind the grille is the condenser fan, with debris against the blade or a bearing wearing out, and a low hum you feel through the cabinets is normally the compressor mounts, which harden over the years and stop isolating anything. A whine that cuts out the moment a door is opened is coming from the evaporator fan inside the compartment, and that fault normally turns up with a temperature complaint alongside it.

What we check, and in what order

Short cycling deserves a call the same week. A compressor draws its heaviest current in the first seconds after it starts, so a unit starting six times an hour is doing far more work than one running steadily, and the winding and the start components are what pay for it. The causes are worth knowing in order: a condenser restricted enough that head pressure trips the overload, a start relay or capacitor that has failed and is dropping the compressor out on thermal protection, or a thermistor telling the control the compartment is at temperature when it is nothing of the sort. The first is a cleaning job and the last is an inexpensive sensor. Which one it turns out to be tends to follow the address: on the water in Coronado, Point Loma or Del Mar the coil is clean of dust and has corroded instead, while inland in Escondido, Poway or Fallbrook it is dust and a hot kitchen doing the restricting. Left alone, all three finish in the same expensive place.

Locating the noise takes about a minute and narrows it further than any description over the phone. Open the door: on most units the evaporator fan stops when the door switch opens, so a sound that vanishes is inside the compartment and a sound that carries on is behind the grille. Then note whether it comes and goes with the compressor cycle or runs continuously, because the condenser fan and the compressor start together while the evaporator fan does not. Those two observations usually put the part on the van before anyone has looked at the appliance.

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