Bosch dishwasher (100/300/500/800/Benchmark): field service manual

Start of cycle: the control usually runs the drain pump briefly to clear the sump, then opens the inlet valve. Fill is metered by a flow meter on the inlet path rather than only by a pressure switch; the control counts the meter's pulses to know how much water came in. Bosch asks for about 10 L/min (about 2.6 gal/min) supply flow; low flow sets fill codes.

Wash: the heat pump circulates water from the sump to the spray arms and heats it as it passes through the built-in heater. An NTC thermistor tells the control the water temperature so it can switch the heater on and off. A diverter (motor-driven on most models) alternates or splits flow between the lower and upper arms.

Soil sensing: on 500/800 and up, a turbidity (optical) sensor in the sump reads how cloudy the water is and the control adds or skips rinses; the 800 series also has an optical Aqua Sensor used to judge cycle end. A dirty or scaled sensor window can stretch or shorten cycles without setting a code.

Drain: the drain pump sits under the filter in the sump and pushes water out through a check valve and the drain hose. Drain-path codes (E24/E6103) and pump-blocked codes (E25/E6102) are the most common Bosch calls.

Dry: there is no exposed element. Final rinse water is heated, the hot stainless tub then condenses moisture as it cools. Upper series add a zeolite mineral pack and drying fan (CrystalDry) that releases heat when it absorbs moisture; the fan has its own code (E07/E2130). Plastics staying wet is normal on condensation dry.

Flood protection: the base pan under the tub has a float (foam block) switch. If water reaches the pan, the float lifts, the AquaStop valve on the supply end of the inlet hose closes and the drain pump runs continuously; the display shows E15/E3100. The pan must be dried and the leak found before the code clears.