Bosch Water Heater Error Codes

4 error codes for Bosch water heater models. Each links to the full diagnostic procedure from the service manual.

CodeDescription

A7Outlet temperature sensor not sensing expected output temperature (status…E9Overheat sensor (ECO) open circuit (resets when cooler temperatures are…EANo flame ionization detected with water flow.ECGas leakage error, gas valve circuit not closing properly.

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A7 on my Bosch Water Heater

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Outlet temperature sensor not sensing expected

From Service Manual 334724, p.16:

1.Check that the sensor is firmly attached to the hot water pipe (see Fig. 70, page 52).

2.Disconnect the sensor and measure resistance at the sensor body. Expected: 10 kΩ to 12 kΩ at 77°F (25°C).

3.Check the sensor harness for opens and shorts. Back-probe the sensor pins at the control board connector; a reading outside 5 kΩ to 50 kΩ indicates a failed sensor.

Part 00617955

Temperature sensor (NTC)

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