Ct,
The water level switch is in control of triggering the motor to turn on for agitation when the target fill level is reached, for either the wash period or the rinse period of the cycle. The fill level is sensed via air pressure which increases (or decreases) in a tube/hose according to the height of the water in the tub. One end of the tube connects at the side of the tub near the bottom, the other end connects to the water level (pressure) switch in the console. The increasing pressure of air caught in the tube as the water rises in the tub makes the switch contacts inside the water level control trigger to turn off the fill and turn on the motor for agitation when the water reaches the selected level.
The machine may immediately begin agitation without water if the water level switch contacts are malfunctioning, i.e. stuck together. If that's the cause of the problem, turning the water level knob back-and-forth several times may (or may not) loosen the stuck contacts.
As RepairGuy notes above, setting the timer for a very short wash time, probably the last 1 to 2 mins of the wash period on the Heavy Duty cycle, may by design have the machine agitate with no water. It should fill at any other timer position in a wash period.
You also need to check for the problem at 1) all three temperature choices in 2) both the Heavy Duty and Permanent Press cycles. Report back whether water does or does not fill in at each temp choice, and whether the water is appropriately hot, warm, or cold if it does fill.
