DMEX / LVDD troubleshooting flow
DISPENSER ISSUE
↓
Identify dispenser number
↓
Is it a card reader / data / video / communication issue?
├─ YES → Check LVDD module for that dispenser
│ ↓
│ Check LVDD motherboard group
│ ↓
│ Check low-voltage input / output path
│
└─ NO → Check DMEX module for that dispenser
↓
Check hook signal
↓
Check E-stop / reset logic
↓
Check pump contactor output
↓
Check breaker / field wiring / STP
Start with LVDD when:
- Card reader is offline
- Video / display is blank
- POS communication is lost
- Low-voltage communication paths are down
Start with DMEX when:
- Dispenser powers up but will not pump
- Reset is not working
- E-stop is active
- Pump request / fueling enable is missing