Hitachi 01001 fault code

What it means

The outdoor unit has seen a supply outside its window. Confirm a stable, in-range mains supply at the outdoor terminals before condemning the board.

Safety: Safe isolation, then TREAT THE DC LINK AS LIVE. The electrolytic capacitors hold a lethal charge after the supply is off. Discharge through a suitable resistor across the + and − terminals and confirm with a meter on DC before touching the board. Never short the terminals with a screwdriver.

Source: Hitachi Technical Catalogue §9.10 / §10.1.2 Error Code Information (RAK-PSES(W)/RAC-WSE — Hitachi UK; RAK-PED/RAC-WED — Hitachi R32 catalogue), both render-verified

UK models this code applies to

Tap yours to open 01001 on that machine.

01001 on these comes from each model's own manual, which may not match the meaning above — tap yours to read it.

Now the harder half: proving what caused it

01001 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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