Sub-Zero 600 Series (601–695)

One series, two generations of control

The 600 Series kept the same cabinets while its electronics changed, and the difference matters more to a repair than the model number does.

Units built before serial number 1810000 have a control that shows temperatures, a flashing SERVICE light and a VACUUM CONDENSER message, and it stores nothing. A technician reads it with a thermometer and a meter.

The later control keeps a table of error codes — EC 05 to EC 50 — that a technician pulls up from the keys in Diagnostic Mode, along with a history of past temperatures. A stored code turns an afternoon of testing into a short list.

The serial number on the tag says which one you have.

The configurations

Over-and-under units put the refrigerator above a freezer drawer: the 611 at 30 inches and the 650 at 36. Side-by-sides run from the 36-inch 661 through the 42-inch 642 to the 48-inch 632. Three carry ice and water in the door: the 42-inch 685, and at 48 inches the 690 and the later 695. The 601R, its glass-door 601RG and the all-freezer 601F are 36-inch single-door columns — and the only models in the series that stand 73 inches rather than 84.

Every combination model has two compressors and two separate refrigeration systems, one for each compartment. That is why one side can fail while the other holds perfectly.

Where a repair happens

The condenser and compressors live behind the top grille, so most repairs never disturb the doors, the panels or the toe-kick. The evaporator fans, sensors, defrost heater and ice maker are reached from inside the cabinet. Pulling a unit out of its opening is the exception, and then the anti-tip blocking at the back of the opening matters.

Parts

Sub-Zero stopped building the 600 Series long ago, so every part is a question for the diagnosis rather than a promise. Some common parts are still sourced; some are not. The model and serial off the tag are what a parts search starts from.