Deep Sea Electronics (DSE) modules—including the DSE7320 MKII, DSE6120, and DSE4520—are among the most widely installed auto-start and auto-mains-failure (AMF) controllers in diesel generator sets globally.
When an alarm triggers or a generator fails to crank during a utility outage, diagnosing the fault quickly is essential. This technical guide outlines the diagnostic procedure for common DSE alarm codes, terminal wiring pinout verifications, and replacement criteria.
1. Understanding DSE Alarm Hierarchy
Deep Sea controllers categorize alarms into three distinct action levels:
- Warning Alarms (Yellow Icon): Non-critical conditions (such as low battery voltage or pre-alarm temperature). The generator continues running, but the LED flashes to alert operators.
- Electrical Trip (Red Icon + Horn): Isolates the load circuit breaker (MCB/GCB opens) and initiates an engine cooling run before shutdown.
- Shutdown Alarms (Red Flashing Icon + Engine Stop): Immediate fuel rack de-energization and crank cutout to protect against catastrophic mechanical or electrical failure.
2. Top 5 DSE Failure Symptoms & Step-by-Step Fixes
Symptom 1: “Fail to Start” / “Fail to Crank” (Crank Failure Alarm)
The controller attempts its programmed cranking cycles (typically 3 attempts of 10s crank / 10s rest), but the engine does not rotate or fire.
Diagnostic Checklist:
- Check the exact variant: Use the installation diagram for the exact controller model and variant; do not infer terminal numbers from another DSE model.
Symptom 2: “Fail to Come to Rest” Alarm
The controller displays this shutdown alarm if it continues detecting engine speed signals after the fuel solenoid de-energizes.
Causes & Solutions:
- Residual MPU Signal: Inspect the magnetic pickup sensor (MPU) wiring. AC noise induced on unshielded cable pairs can trick the module into seeing phantom RPM.
- Alternator Charge Excitation (WL Terminal): Disconnect the D+ / WL wire from the engine charging alternator. A faulty diode in the engine charging alternator can leak AC voltage onto the sensing pin.
Symptom 3: Low Oil Pressure / High Engine Temperature Trip on Startup
The engine starts but shuts down within 10–15 seconds, flashing an oil pressure or coolant sensor alarm.
Causes & Solutions:
- Oil Pressure Delay Timer: Check the “Oil Pressure Delay” setting in DSE Configuration Suite software (recommended: 10–15 seconds). This allows the mechanical pump to build pressure before safety monitoring activates.
- Sender Curve Mismatch: DSE controllers support resistive senders (VDO, Datcon, Murphy, PT100). If a 10-bar sender is configured with a 5-bar resistance curve, the controller reads incorrect pressure values.
Symptom 4: Under Frequency (Hz) / Under Speed Shutdown
The generator starts and runs, but shuts down after the warm-up timer expires with an under-frequency alarm.
Causes & Solutions:
- Speed Governor Calibration: Check the engine speed governor (such as the ESD5500E). Confirm the engine reaches the rated speed specified for the generator system before troubleshooting a persistent under-frequency alarm.
- AVR Sensing Voltage Loss: If the automatic voltage regulator (AVR) fails to build nominal voltage, the controller may not detect AC frequency via the alternator stator terminals.
3. Key DSE7320 MKII Terminal Pinout Quick Reference
The terminal labels below transcribe the newer DSE7310-20-MKII reference. Confirm the exact module variant before wiring: pins 38–41 are mains-voltage sensing on the DSE7320 MKII and are marked not applicable for the DSE7310 MKII.
| Pin(s) | Function stated in the reference |
|---|---|
| 1–2 | DC Supply |
| 3 | Emergency Stop |
| 4 | Fuel |
| 5 | Start |
| 6 | Charge Alternator |
| 7 | Not Applicable |
| 8–13 | Digital Outputs |
| 14–20 | Analogue Inputs |
| 21–23 | Magnetic Pick-Up |
| 24–29 | Engine ECU/ECM |
| 30–31 | Normally Closed Volt Free Output |
| 32–33 | Normally Open Volt Free Output |
| 34–37 | Generator Voltage Sensing |
| 38–41 | Mains (Utility) Voltage Sensing (DSE7320 MKII only; not applicable on DSE7310 MKII) |
| 42–47 | Generator Current Sensing |
| 48–55 | Digital Inputs |
| 56–58 | RS485 |
4. When to Replace the Controller
If terminal voltages, external relays, and configuration files are verified but the controller exhibits any of the following symptoms, internal microprocessor or relay degradation has occurred:
- Unresponsive LCD Display or Blank Screen with healthy 12V/24V on pins 2 and 3.
- Shorted Output Drivers: Fuel or Crank outputs remain permanently energized even in Stop mode.
- Internal Memory Corrupted: The unit displays “Config Corrupt” or fails firmware download via USB.
Interchangeability is not established by the newer reference document. Verify the exact module variant, panel cut-out, wiring diagram, engine interface and configuration before any replacement.
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