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EEV Stepping Motor Diagnosis — Coil Resistance, Back-EMF, Signal Check
Likely causes
Measure 4-phase coil, signal, and back-EMF
Check: EEV coil = 4-phase stepper motor (usually 5 wires: 1 common + 4 phases). Measure resistance from common to A/B/C/D = 40–60 Ω each (manual prevails). Any phase open (∞) or short (0 Ω) = coil bad. **Force signal from PCB**: with system OFF, send 0%/100% commands → hand on coil should feel 4 'click' vibrations (one per phase). No vibration = PCB signal fault. Vibration present but no operation = slide stuck inside body.
What to do: **Coil open/short → replace coil only** (keep body, same-spec OEM). Residential KRW 10–50k. **No PCB signal → PCB-side EEV driver IC or transistor fault** = replace PCB or repair shop. **Body slide stuck → recover → cut/replace body → vacuum → charge**. Residential body KRW 100–200k. After replacement = activate PCB learning mode per maker manual.
**Field trick**: EEV failure is rare but diagnosis tricky. **Feeling 'click' vibration on coil = coil OK + PCB signal OK** simultaneously — the trick. If both OK at once, body fault confirmed. With system OFF, hand on EEV body should feel slight vibration/warmth in normal state. R-32 systems = A2L, anti-static wrist strap required when working on EEV.
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