RSSI too low in cabinet

How it presents

Display

RSSI too low in cabinet

Symptom

RSSI too low in cabinet on sierra-wireless (airlink): AirLink ALEOS / LED pattern shows MDM-RSSI. Techs see session abort or stall Unavailable until the ranked cause is cleared. Correlate Modem signal log + OCPP disconnect timestamps before opening the cabinet.

Root causes (by observed frequency)

1. #1 Backhaul or CSMS path instability for MDM-RSSI

   DNS, TLS, NAT keepalive, and MTU before board RMA

2. #2 Wrong OCPP URL / chargePointIdentity after board or SIM swap
3. #3 CSMS-side rate limit or Auth storm after mass reconnect

Diagnostic procedure

1. 1. Capture AirLink ALEOS / LED pattern message for MDM-RSSI, connector ID, and last successful session time

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

   Tools: phone photos (scrubbed), CSMS

2. 2. Pull Modem signal log + OCPP disconnect timestamps; confirm whether RSSI too low in cabinet follows one gun, one cabinet, or the whole site

   Expected: Fault correlates to one path

   Tools: CSMS export, OEM cloud

3. 3. On model airlink hardware, isolate power quality / protective devices before opening HV for MDM-RSSI

   Expected: Voltage in band; no unexpected trips

   Tools: DMM, IR gun, LOTO kit

4. 4. Execute rank-1 cause check for “RSSI too low in cabinet”; 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 MDM-RSSI evidence pack (HMI photo, OCPP snippet, readings) — RSSI ok ≠ stable websocket — check MTU, NAT, and keepalives

   Tools: ticket template

The fix

Clear MDM-RSSI (RSSI too low in cabinet) by correcting the ranked cause on sierra-wireless / airlink, then run a full validation session.

• Modem / SIM / antenna path

  Verify APN and CSMS URL after modem swap

• Suspect module or controller indicated by rank-1 cause

  OEM sierra-wireless service channel; keep serial for RMA

  MDM-RSSI

1. LOTO and verify zero energy per sierra-wireless HV procedure before any bus work
2. Correct rank-1 cause for MDM-RSSI; 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