Hi everyone,
I have a Bosch no-frost fridge/freezer, model KSU36620NE/18, FD8302. It is in very clean condition and was previously used only seasonally. I received it from a relative after it failed and was replaced.
I am trying to repair it. I replaced the mainboard with a new board that was sold to me as identical/compatible, but the cooling cycle is still not behaving correctly.
The main problem seems to be that the refrigerator section temperature is not being interpreted correctly by the control board. I cannot measure subzero freezer temperatures accurately, so I am not sure if the freezer control is also affected.
What happens:
- The unit can cool both sections.
- The fan runs for a while, then stops.
- After that, the fan does not restart when it should.
- Changing the temperature setting does not seem to influence the fan correctly.
Examples:
- If the fridge section is around +5°C and I lower the target to +2°C, the fan does not start, even after power cycling the unit.
- If the fridge section is around +4°C and I raise the target to +6°C, the fan may still run anyway.
So the board does not seem to react logically to the actual fridge temperature or the selected target temperature.
Because of this, I suspect one of these:
- Fridge temperature sensor / NTC problem
- Sensor wiring or connector pinout mismatch
- Wrong or incompatible mainboard despite being sold as compatible
I am planning to order a new temperature sensor from the same website that sold me the motherboard.
Board and cable connector lineup:
https://iili.io/CiTOG5u.jpg
Cable connection to the new motherboard. Notice the extra pin on the right that is not connected:
https://iili.io/CiTNl9a.jpg
The large harness connector has some empty pin positions. Is this normal for this model?
The fan seems to be a 220-240V fan. Would it be a reasonable temporary workaround to power the fan independently using a thermal AC switch?
https://iili.io/CiTLKPe.webp
Or would that not work properly if this model has an air damper/flap controlled by the mainboard?
Any advice from someone familiar with Bosch KSU models would be appreciated.
⟐ Commented August 15, 2026 at 19:17 MST
Hi everyone, I have a Bosch no-frost fridge/freezer, model KSU36620NE/18, FD8302. It is in very clean condition and was previously used only seasonally. I received it from a relative after it failed and was replaced. I am trying to repair it. I replaced the mainboard with a new board that was sold to me as identical/compatible, but the cooling cycle is still not behaving correctly. The main problem seems to be that the refrigerator section temperature is not being interpreted correctly by the control board. I cannot measure subzero freezer temperatures accurately, so I am not sure if the freezer control is also affected. What happens: - The unit can cool both sections. - The fan runs for a while, then stops. - After that, the fan does not restart when it should. - Changing the temperature setting does not seem to influence the fan correctly. Examples: - If the fridge section is around +5°C and I lower the target to +2°C, the fan does not start, even after power cycling the unit. - If the fridge section is around +4°C and I raise the target to +6°C, the fan may still run anyway. So the board does not seem to react logically to the actual fridge temperature or the selected target temperature. Because of this, I suspect one of these: - Fridge temperature sensor / NTC problem - Sensor wiring or connector pinout mismatch - Wrong or incompatible mainboard despite being sold as compatible I am planning to order a new temperature sensor from the same website that sold me the motherboard. Board and cable connector lineup: https://iili.io/CiTOG5u.jpg Cable connection to the new motherboard. Notice the extra pin on the right that is not connected: https://iili.io/CiTNl9a.jpg The large harness connector has some empty pin positions. Is this normal for this model? The fan seems to be a 220-240V fan. Would it be a reasonable temporary workaround to power the fan independently using a thermal AC switch? https://iili.io/CiTLKPe.webp Or would that not work properly if this model has an air damper/flap controlled by the mainboard? Any advice from someone familiar with Bosch KSU models would be appreciated.
Is this a good question?
Score 0
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