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Fujitsu Waterstage 6/7 fault code

Fujitsu Waterstage heat pumps

What the Fujitsu Waterstage 6/7 fault code means, from the manufacturer's own service literature, and the UK models it applies to.

What it means

Outdoor unit power short interruption error (protective operation)

Outdoor unit power short interruption error (protective operation)

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

Tap yours to open 6/7 on that machine.

Now the harder half: proving what caused it

6/7 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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