Unit displays Code 73 and will not operate

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 or jumper settings, Faulty wiring between main board and sub-boards, Defective control board

Safety first: Turn OFF power and gas before accessing the control board.

Steps to check:

Verify dip switch settings: Compare the dip switch positions on the control board with the Rinnai installation manual for your model and gas type.
Inspect board connections: Ensure all ribbon cables and connectors between boards are fully seated.
Reset the unit: After corrections, restore power and gas and reset.

When to call a professional: If Code 73 remains, the control board or communication harness may need replacement by a technician.

Hard 4/5

Main Control Board

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