Fujitsu Waterstage 10/4 fault code

What it means

Outdoor unit pressure error

Source: Fujitsu Waterstage Super High Power D&T Manual, §Control System pp.03-3…03-5 — numeric display codes, interface-card LED pairs and outdoor-board flash counts with the published decode procedure

UK models this code applies to

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Now the harder half: proving what caused it

10/4 names a symptom, not a root cause. In the app, the same code opens a guided investigation: what to measure first, the expected values for your exact model, and an honest verdict — including “nothing in this machine is broken” when that's what the readings say.

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