NACS thermal derate to zero

How it presents

Symptom

NACS thermal derate to zero (NACS-H03) — NACS path field fault. Stay OEM-agnostic until the protocol stage pins a hardware path; capture SECC/OCPP/vehicle evidence before opening the cabinet.

Root causes (by observed frequency)

1. #1 Primary nacs path cause for NACS-H03: NACS thermal derate to zero

   Stage-pin before hardware RMA

2. #2 Cable/vehicle/adapter contribution proven by known-good swap
3. #3 CSMS/SECC/config mismatch after update or board swap
4. #4 True EVSE hardware failure after protocol path is proven clean

Diagnostic procedure

1. 1. Capture NACS path stage evidence for NACS-H03 (HMI, OCPP/SECC logs, connector ID)

   Expected: Exact fail stage

   Tools: phone, CSMS, SECC logs

2. 2. Decide one gun vs cabinet vs site vs vehicle cohort

   Expected: Fault boundary

   Tools: CSMS timeline

3. 3. Known-good cable/vehicle prove appropriate to “NACS thermal derate to zero”

   Expected: Follows cable/vehicle or stays

   Tools: known-good

4. 4. Correct config/CSMS/SECC settings indicated by the stage

   Expected: Stage advances

   Tools: HMI, CSMS admin

5. 5. Escalate OEM hardware only with stage-pinned evidence pack

   Tools: ticket

The fix

Clear NACS-H03 by pinning the nacs path stage and fixing that cause — not shotgun EVSE modules.

• Assembly indicated only after stage pin

  OEM-agnostic until proven

1. Pin the nacs path fail stage for NACS-H03 before ordering modules.
2. Correct the ranked cause for “NACS thermal derate to zero” (cable, vehicle, config, or CSMS/SECC).
3. Clear latches and restore Availability only after the cause is removed.
4. Validate a full session through the previously failing stage.
5. Attach scrubbed protocol traces and photos to the confirmation ticket.