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Error code reference

Bosch Washer Error Code F:28

Error of flow sensor

Bosch codesBosch washer codes

Error of flow sensor — provides implausible values; water intake changes from volume-based to time-based.

First step from the service manual

Check flow sensor, check wire harness.

The complete diagnostic procedure includes additional test steps, resistance specifications, wiring diagram references, and component test points.

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What F:28 means on a Bosch washer

The F:28 error code on a Bosch washer indicates that the flow sensor is producing implausible values, meaning the control board is receiving readings that fall outside the expected parameters for normal water intake. The flow sensor, also called a water flow meter, monitors the volume of water entering the drum by measuring flow rate. When the sensor output becomes erratic or unreadable, the control board loses confidence in volume-based fill measurements and automatically switches water intake from volume-based control to time-based control as a fallback mode.

This fault most commonly originates from a damaged or clogged flow sensor, poor electrical connections along the wire harness, or internal sensor failure. The flow sensor is typically installed in the cold water inlet path and uses a rotating paddle or turbine mechanism to generate pulse signals proportional to water volume. Debris, limescale buildup, or a seized rotor can disrupt these pulse signals, causing the control board to register the values as implausible.

Diagnosis should begin by inspecting the wire harness connecting the flow sensor to the main control board. Check for damaged insulation, corroded terminals, or loose connectors. If the wiring is intact, the flow sensor itself should be tested or replaced. Operating in time-based fill mode may result in inconsistent water levels and wash performance, so resolving this fault promptly is recommended.

Source: manufacturer service documentation.

Common causes of F:28

  1. 01

    Clogged or seized flow sensor

    Part replacement

    Limescale, sediment, or debris can block the sensor's internal rotor, preventing it from spinning freely and generating accurate pulse signals. Inspect the sensor for buildup or a stuck turbine mechanism.

  2. 02

    Damaged or loose wire harness

    Wiring / connection

    The wiring connecting the flow sensor to the control board may have corroded terminals, broken wires, or loose connectors that interrupt the signal. Visually inspect the harness and wiggle connectors while monitoring for intermittent faults.

  3. 03

    Failed flow sensor

    Part replacement

    Internal failure of the sensor's electronic or mechanical components can cause it to output erratic or no signal at all. If the harness checks out, the sensor itself likely needs replacement.

  4. 04

    Low water pressure affecting sensor readings

    Wiring / connection

    Insufficient water supply pressure can cause the sensor rotor to spin irregularly, producing pulse signals outside the expected range. Verify that household water pressure meets the washer's minimum requirements and check inlet screens for blockage.

  5. 05

    Control board fault

    Part replacement

    In rare cases, the main control board may misinterpret valid sensor signals due to a board-level failure. This should only be considered after the sensor and harness have been tested and confirmed good.

See the test procedure for each cause

Frequently asked questions about F:28

What does F:28 mean on a Bosch washer?
F:28 means the flow sensor is providing implausible values that the control board cannot use reliably. In response, the washer automatically switches from volume-based water intake to time-based water intake as a fallback. The error typically points to a faulty flow sensor, a wiring issue, or debris blocking the sensor's rotor.
Can I fix the F:28 error myself?
Some causes of F:28 are DIY-friendly, such as inspecting and reseating wire harness connectors or cleaning a debris-clogged flow sensor. If the sensor itself has failed internally, replacing it requires basic disassembly of the washer and comfort working with electrical connectors. If you are unsure about working with appliance wiring, a qualified technician should perform the repair.
Is it safe to keep using my Bosch washer with an F:28 error?
The washer will attempt to continue operating using time-based water fill as a backup, but water levels may be inconsistent, which can affect wash quality and in some cases overload or underload the drum. Continuing to run cycles with this fault is not recommended for extended periods. Resolving the underlying sensor or wiring issue promptly will restore normal operation.
How much does it cost to fix a Bosch washer F:28 error?
If only the wire harness needs repair or reconnection, costs may be minimal, covering only a service call if a technician is involved. Replacing the flow sensor typically costs between $50 and $150 for the part, plus labor if a technician performs the work. A full diagnostic service call and repair could range from $100 to $300 or more depending on your location and the extent of the damage.
Will resetting the washer clear the F:28 error?
Resetting the washer may temporarily clear the F:28 code from the display, but if the underlying cause, such as a faulty sensor or damaged harness, has not been addressed, the error will return during the next fill cycle. A reset is useful for confirming whether the fault is intermittent or persistent, but it does not fix the hardware problem causing the error.

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