Bosch Configuration / Parameter Fault

Furnace shows U9; may indicate incorrect configuration or parameter error

This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.

If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.

Possible Causes

Incorrect DIP switch settings, Wrong gas type configuration, Corrupted parameter memory, Incompatible control module

Safety: Disconnect power before adjusting internal switches.

Check DIP switches/jumpers: Compare the positions on the main PCB to the Bosch installation manual for your model and gas type.
Factory reset: Some Bosch controls allow a parameter reset to factory defaults via the service menu. Only perform this if you have the manual and can re-enter required settings.

Incorrect configuration can lead to unsafe operation. If unsure, contact a Bosch-trained technician.

Hard 4/5

Main Control Board

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