Isolation fault after cable swap

How it presents

Symptom

Express 250 isolation fault before or during CableCheck after a cable swap, rain, or cooled-cable service — one gun or whole power cabinet. chargepoint field note: keep evidence scrubbed and prove the ranked cause before module RMA on CP-E250-ISO.

Root causes (by observed frequency)

1. #1 Moisture or damaged insulation on the failing DC cable/gun

   Known-good cable before power-stage blame

2. #2 Coolant contamination at quick-connects after cable service
3. #3 Shared cabinet ISO measurement upset by a second wet path
4. #4 ISO board / measurement fault after surge or harness damage

Diagnostic procedure

1. 1. Capture HMI isolation string and connector ID; one gun vs cabinet

   Expected: Scope of fail

   Tools: phone, Cloud

2. 2. Dry cable/gun; known-good cable prove on failing dispenser

   Expected: Fault moves with cable or stays

   Tools: known-good cable

3. 3. Inspect cooled-cable quick-connects for residue if recently serviced

   Expected: No glycol film on HV seals

   Tools: IR, rags

4. 4. LOTO before any HV ISO board work; check harness seating

   Expected: Connectors fully seated

   Tools: LOTO kit

5. 5. OEM ISO service only after dry known-good cable fails

   Tools: ChargePoint

The fix

Cable/moisture first on Express 250 isolation; shared coolant quirks before ISO board crates.

• DC cable / ISO assembly

  Match cooled spec

1. Stop spamming isolation clears into a wet fault. Document readings and scrubbed photos for CP-E250-ISO before closing the ticket.
2. Dry and prove with a known-good cable on the failing gun.
3. Address coolant contamination at quick-connects if present.
4. LOTO and reseat ISO harness only after the cable path is clean.
5. OEM ISO assembly last with scrubbed photos. Document readings and scrubbed photos for CP-E250-ISO before closing the ticket.