Bosch
Tankless Water
Heater
Control Unit Problem.
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Before you change your electronic control unit (Bosch Aquastar 125FX
Electric Control Box Part number 8707207106) on
your Bosch tankless water heater 125FX Aquastar. Check the wiring
harness that goes to the overtemperature sensors. My tankless
heater gave the same symptoms as the trouble
shooting
guide (TWH-G1-18_No_spark_with_water_flow.pdf)
provided
by
Bosch, BUT it was not the control box. The wiring
harness was shorted to the heater's chassis. See photos below:
