Progressive wear on the Victron MultiPlus 3-way switch (I · II · O). Internal contact degrades over time due to thermal expansion under load. Switch appears to engage in position I but loses internal contact after 5 minutes of operation, causing VE.Bus dropout and Cerbo GX to lose visibility of the unit. Contributing factors: (1) Input current limit set too high (24A) for marina supply, causing L2 phase to draw 33A and inlet temperature to reach 71°C — above safe threshold. (2) VE.Bus errors were logged from January 2023 but not investigated, allowing fault to progress undetected for over 3 years. (3) Unit age 4 years 1 month — end of service life for switch mechanism. A straight switch replacement is insufficient given the fault history — full unit replacement is recommended.

PHASE 1 — Immediate stabilisation: 1. Disconnect shore power at the marina pedestal. Inspect the CEE shore connector for burn marks or melted contacts — do not reconnect through a damaged connector. 2. Set Multiplus input current limit to 16A per phase in the Victron app before reconnecting. 3. If panel button is not accessible, set the 3-way switch to position II (Charger Only) as a temporary bypass. Position I is the correct operating mode — position II is a diagnostic workaround only. 4. Reconnect shore power and monitor inlet temperature for the first 15 minutes. PHASE 2 — VE.Bus dropout diagnosis: 5. If Multiplus drops off VE.Bus after a few minutes of charging, check RJ45 VE.Bus cables at both ends — Multiplus and Cerbo GX — confirm fully seated. 6. Check VE.Bus circuit breaker — confirm in up (on) position. 7. If cables and breaker are clear and dropout continues, fault is at the switch mechanism — thermal expansion causing contact loss under load warmth. This is a known progressive wear fault. 8. Cycling the switch (O — wait 10 seconds — I) may restore briefly but fault will recur. This is not a fix. PHASE 3 — Remote service via OKi: 9. WMC Engineer connects remotely via Tailscale to OKi live data. 10. OKi runs VE.Bus diagnostic — confirms fault originates at Multiplus side, not Cerbo, not cable, not breaker. 11. OKi pulls unit serial number, manufacture date, installation date, and full alarm history from Victron VRM. 12. If VE.Bus error history shows recurring events over multiple years with increasing frequency, classify as end of life — do not repair only. 13. Generate WMC Remote Service Report and distribute to wybo.overmeer@wmc.services and vessel owner. PHASE 4 — Unit replacement: 14. Order like-for-like replacement — Victron MultiPlus 24/3000/70-50 (or current installed spec). Like-for-like requires no rewiring — direct swap. 15. Temporary state until technician arrives — Multiplus off (position O), shore power connected but not charging, battery on DC discharge, OKi monitoring SoC, alert armed at 40%. 16. Set annual inspection reminder for all Multiplus units on this vessel — arm at 12-month intervals. 17. After replacement — confirm VE.Bus communication restored in Cerbo GX device list before closing case.