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Not lit DEFROST (green)

LED: DEFROST (green) Not lit — Neither defrosting nor protection is active

NIBE · S2125 Air/Water Heat Pump

What does Not lit DEFROST (green) mean?

The green DEFROST LED on the base board (AA2) is not lit, which is the normal indication when no defrosting or protection functions are currently active.

Common Causes

  • Normal operating condition.

Repair Steps & Checklist

Click steps to track your progress.

  1. 1

    No action needed for this LED state.

  2. 2

    If the system is expected to be defrosting or experiencing issues like ice build-up, check other indicators or settings.

Browse all codes in this manual (55)
Verified technical data. Last updated: April 2026

Related Faults

Communication fault to Inverter 254Alarm 254 (or 264, 203) Communication fault to Inverter — Inverter unpowered or brokenCompressor speed too low 354Alarm 354 (or 503, 186) Compressor speed too low — Inverter safety function reduces compressor speedContinuous light CPULED: CPU Continuous light — CPU is not running correctly
Source: NIBE S2125 Air/Water Heat Pump
Open Manual (Page 32)Search more codes in this manual