Bosch Washer Error Code 27

Error code 27 on a Bosch washer indicates a failure in the offset adjustment calibration of the analogue pressure sensor, also known as the water level sensor or pressure switch. This sensor is responsible for measuring water pressure inside the drum to determine the fill level during each wash cycle. The control board performs an offset calibration check at the start of operation, comparing the sensor's baseline signal to expected parameters. When the sensor produces a signal that falls outside the acceptable calibration range, the board registers this as an offset adjustment error and displays code 27.

The pressure sensor in these machines is typically a small electronic transducer connected to an air trap or pressure chamber at the base of the tub via a thin rubber hose. It sends a variable voltage or frequency signal to the control board based on air pressure changes caused by rising water levels. When the sensor is broken or its signal is drifting out of calibration range, the board cannot accurately determine how much water is in the drum, which makes it unsafe to continue the cycle. A faulty sensor can produce readings that are too high, too low, or erratic, all of which trigger the offset error.

Diagnosing this error begins with a physical inspection of the pressure sensor itself and the wiring harness connecting it to the main control board. Damaged, corroded, or disconnected wiring can mimic a failed sensor, so the harness should be checked for continuity and secure connections before condemning the sensor. If the wiring checks out, the sensor itself is the most likely failed component and will typically require replacement to resolve the error.