The Instant Water Heater is an OEM part for Bosch dishwashers. It is responsible for heating the water to optimal temperatures during the cleaning cycle through its internal heating element and thermostat.  Causes of failure can be attributable to scale build-up over time inhibiting heat transfer, cracks in heating elements, or thermostat malfunctions. Symptoms of a bad water heater include: Incomplete cleaning even on high-temperature cycles Dishes not reaching appropriate sanitization temperatures Hot water not dispensing properly during the cycle Slow water heating causing extended cycle times This genuine OEM Bosch part is also compatible with Thermador, Gaggenau and select Kenmore models.This part fixes the following symptomsNot drying dishes properlylights flashing or blinkingPart Number 00219639 (AP2825912) replaces 1097478, 219639, AH3445638, EA3445638, PS3445638, PS8699474.