Bosch A01 (5273)

Critical

Compress — Z1 phase monitor tripped: one or more supply-voltage phases are missing (compressor control/supply). Check that all phases are present and carry voltage.

Bosch A01 (5273): Z1 phase monitor tripped: one or more supply-voltage phases are missing (compressor control/supply). Check that all phases are present and carry voltage. This fault typically halts operation and needs immediate attention.

Possible causes

Heat pump fuse tripped.
Phase(s) missing at supply terminals.

Check steps

Measure all three phases at terminals.
Check fuses; if voltage at EMI filter, check inverter.

Affected parts

Sicherungen
Inverter

Safety note

400 V three-phase – qualified electrician only.

Source: Bosch resmi servis kılavuzu — DÜZELTİLDİ: Bosch official error-code lookup tool (bosch-homecomfort.com/de/de/wohngebaeude/service-und-support/bosch-fehlercode-suche/errorcode?query=5273), cross-checked against GitHub regofetcher/IVT_errorcodes.json (description match for phase-loss alarm, code 5273).

Reviewed by Anıl Güzeldemir — in the refrigeration machine room since 2006, developer of Enthalio.

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