1
Communication error indoor↔outdoor (E6/E7/P4 etc.)
highCheck24 V AC or DC on comm wire between S1/S2/S3; check for reversed L/N.
FixFix wiring polarity; replace comm cable if damaged.
2
Low charge / line-set leak at flare
highCheckBubble-test flares; superheat.
FixRe-flare with proper tool and torque; evacuate to 500 µm; weigh in charge.
ToolsFlaring tool · Torque wrench · Micron gauge
3
Indoor blower motor / wheel binding
medCheckTurn wheel by hand; check DC bus voltage on inverter board.
FixReplace motor; clean wheel.
Safety
Pull the disconnect and lock out before opening HVAC equipment. Discharge dual-run capacitors before handling. Refrigerant recovery and brazing require EPA 608 certification and proper PPE.