Bosch Refrigerator Error Code FD

The FD code on a Bosch refrigerator indicates that the freezer defrost sensor, known as the FD-sensor, has either become disconnected or has developed a short circuit. This sensor is located on the evaporator coil in the freezer and monitors temperature during the defrost cycle. The main PCB detects the fault by identifying an abnormal resistance reading in the sensor circuit and triggers the FD error code in response.

Continued use with an FD error is not recommended for the long term, because the defrost cycle may not operate correctly without a functioning FD-sensor. This can lead to frost buildup on the evaporator coil, reduced cooling efficiency, and potential food spoilage. It is best to address the fault promptly to prevent secondary damage to other refrigerator components.

A power reset may temporarily clear the FD code from the display, but the error will return if the underlying sensor fault has not been corrected. The main PCB continuously monitors the FD-sensor circuit during operation, so any ongoing disconnection or short circuit will retrigger the fault. A permanent resolution requires confirming the sensor resistance is within normal range, which means repairing or replacing the faulty sensor or wiring.

A knowledgeable DIYer with a multimeter can perform the initial diagnostic by separating connector CN15 from the main PCB and measuring resistance across the FD-sensor terminals. If the reading confirms an open or short circuit, the FD-sensor on the evaporator must be replaced. Accessing the evaporator typically requires removing freezer shelving and panels, so comfort with appliance disassembly is necessary. If the wiring or connector appears damaged rather than the sensor itself, a repair may be possible without ordering parts.

Repair costs vary depending on whether only the sensor needs replacement or if additional wiring or board work is required. The FD-sensor part itself is generally a low-cost component, typically in the range of $15 to $50. If a technician is hired for diagnosis and replacement, total service costs including labor commonly fall in the range of $100 to $250 depending on your location and service provider.