Bosch Hood Error Code Three speed LEDs blinking

When three speed LEDs blink simultaneously on a Bosch range hood, the control system is reporting a heat sensor protection fault. The over-temperature protection circuit relies on a dedicated heat sensor to monitor internal temperatures and prevent damage to the hood's electronics and motor from excessive heat. When this sensor fails or produces a signal outside the expected parameters, the hood recognizes that it can no longer reliably protect itself from overheating and triggers the blinking LED fault indication.

The heat sensor on these Bosch hoods is not a standalone serviceable component. It is integrated directly into the input board (also referred to as the control or PCB input board), meaning the sensor and the board share a single assembly. A failure can result from physical damage to the board, thermal stress that degrades the sensor over time, a manufacturing defect, or a wiring issue affecting communication between the sensor and the control logic. Because the sensor cannot be tested or replaced independently, diagnosing the fault always leads to evaluating the entire input board.

When this fault is active, the hood's over-temperature protection is non-functional. The control system correctly prevents normal operation by flagging the fault through the LED blinking pattern. Resetting power to the unit will not resolve the underlying fault, as the sensor defect is hardware-based. The correct repair path is replacement of the complete input board assembly, which restores both the sensor function and the protection circuit.