Main DC contactor welded

How it presents

Symptom

Main DC contactor welded — weld detect or stuck-closed feedback after high-cycle use; do not force energy. site-generic field note: keep evidence scrubbed and prove the ranked cause before module RMA on CTR-WELD.

Root causes (by observed frequency)

1. #1 Welded main DC contactor faces after high cycle count

   Prove site stack before OEM module RMA

2. #2 Installation/commissioning mismatch exposed under load
3. #3 Sensor/feedback false alarm after harness work
4. #4 True component failure after the above are excluded

Diagnostic procedure

1. 1. Capture indicators/alarms for CTR-WELD and whether one stall or whole pad

   Expected: Scope

   Tools: phone, LMS

2. 2. Correlate with LMS/feeder/BESS events at the same timestamp

   Expected: Upstream coincidence?

   Tools: SCADA

3. 3. Execute site-side checks for “Main DC contactor welded” before opening EVSE HV

   Expected: Site cause found or cleared

   Tools: DMM, IR, electrician

4. 4. Known-good stall/cable prove when applicable

   Expected: Follows asset or site

   Tools: known-good

5. 5. Escalate OEM EVSE only with site path proven healthy

   Tools: ticket pack

The fix

Clear CTR-WELD (Main DC contactor welded) by proving and fixing the site/stack cause before EVSE module swaps.

• Site component indicated by rank-1 cause

  Match one-line / OEM site gear

1. Treat CTR-WELD as a site/stack fault until the feeder/LMS/cooling path is proven.
2. Correct the ranked site cause with the responsible trade (electrician, controls, cooling).
3. Restore interlocks and protective devices — never defeat them.
4. Retest EVSE sessions only after site allocations and voltages look sane.
5. Hand OEM a scrubbed evidence pack if the fault remains with a healthy site.