Main DC contactor welded

How it presents

Display

Main DC contactor welded

Symptom

Main DC contactor welded on site-generic: Site LMS / breaker / skid local indicators shows CTR-WELD. Techs see session abort or stall Unavailable until the ranked cause is cleared. Correlate Site BMS / LMS / SCADA if present before opening the cabinet.

Root causes (by observed frequency)

1. #1 Interlock / contactor feedback disagreement for CTR-WELD

   Door, E-stop, weld-detect, and aux contacts — verify loop continuity

2. #2 Welded or slow contactor after high-cycle depot use
3. #3 PLC / controller false detect after harness re-seat

Diagnostic procedure

1. 1. Capture Site LMS / breaker / skid local indicators message for CTR-WELD, connector ID, and last successful session time

   Expected: Exact display string + OCPP status/errorInfo if present

   Tools: phone photos (scrubbed), CSMS

2. 2. Pull Site BMS / LMS / SCADA if present; confirm whether Main DC contactor welded follows one gun, one cabinet, or the whole site

   Expected: Fault correlates to one path

   Tools: CSMS export, OEM cloud

3. 3. On hardware, isolate power quality / protective devices before opening HV for CTR-WELD

   Expected: Voltage in band; no unexpected trips

   Tools: DMM, IR gun, LOTO kit

4. 4. Execute rank-1 cause check for “Main DC contactor welded”; swap known-good cable/gun or stall if available

   Expected: Fault moves with cable or stays with cabinet

   Tools: known-good cable, IR, OEM service menu

5. 5. If unresolved, escalate with CTR-WELD evidence pack (HMI photo, OCPP snippet, readings) — Prove upstream site stack before blaming EVSE OEM

   Tools: ticket template

The fix

Clear CTR-WELD (Main DC contactor welded) by correcting the ranked cause on site-generic, then run a full validation session.

• Suspect module or controller indicated by rank-1 cause

  OEM site-generic service channel; keep serial for RMA

  CTR-WELD

1. LOTO and verify zero energy per site-generic HV procedure before any bus work
2. Correct rank-1 cause for CTR-WELD; do not shotgun-replace modules
3. Clear fault latches in HMI/CSMS; confirm StatusNotification returns to Available/Preparing as appropriate
4. Run validation: authorize → handshake → ≥5 minutes energy → clean stop; capture MeterValues
5. Document firmware, part lots, and scrubbed HMI photos for confirmations