Lennox E3

Critical

Mini-Split MWM/MPA (Außeneinheit) — Communication error between outdoor unit main control and integrated power module (IPM), no feedback for 60 seconds.

Lennox E3: Communication error between outdoor unit main control and integrated power module (IPM), no feedback for 60 seconds. This fault typically halts operation and needs immediate attention.

Possible causes

Signal wire between IPM and main board loose/faulty or IPM faulty.

Check steps

Check signal wire (expect ~5V / ~12V DC); if it persists, replace IPM, then main board.

Affected parts

IPM-Modul
Signalkabel

Safety note

Discharge capacitors, isolate power.

Source: Lennox Mini-Split Systems Service Manual — Indoor and Outdoor Unit Error Codes (Corp. 1816-L7, 2018), "Extended Reference Guide - Outdoor Unit Error Codes" §4 and "Indoor Unit Error Codes" §5

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

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Related fault codes

Outdoor EEPROM malfunction — main control boarE0 Indoor unit coil outlet temperature sensor (T2E4 Outdoor coil sensor (T3) error — voltage outsiF1 Outdoor ambient sensor (T4) error — voltage ouF2 Compressor discharge sensor (T5) error — voltaF3 High or low voltage protection active.E5