Overview #
Ocean Alexander yachts equipped with Offshore Systems UK Fuel and Water Level Senders utilize an integrated diagnostic LED to assist with troubleshooting tank level monitoring issues.
The diagnostic LED provides valuable information regarding the sender’s operating status and helps identify whether a problem is related to:
- Sender power supply.
- NMEA 2000® network communication.
- Tank type configuration.
- Calibration.
- Physical sender condition.
Before removing or replacing a sender, use the diagnostic LED as the first troubleshooting step to determine the source of the issue.
Reading the Diagnostic LED #
The sender LED communicates system status through specific flash patterns and colors.
| LED Behavior | Meaning / Recommended Action |
|---|---|
| LED does not flash | Check network power supply or verify the Tank Type switch is set to a valid position. |
| LED flashes rapidly | NMEA 2000® network termination issue or no other active NMEA 2000® device detected on the network. |
| LED flashes once every 2.5 seconds | Normal operation in Level Mode. |
| LED flashes twice every 2.5 seconds | Normal operation in Volume Mode. |
| LED remains ON for approximately 2 seconds | Calibration magnet detected. |
| Red LED ON or flashing intermittently | Short circuit detected. Inspect end cap and sleeve condition. |
Troubleshooting Procedures #
LED Does Not Flash #
A non-flashing LED typically indicates a power or configuration issue.
Check:
- NMEA 2000® network power.
- Network connections.
- Tank Type switch position.
- Sender electrical connections.
Verify the sender is receiving proper network power before replacing the unit.
Rapid LED Flashing #
A rapidly flashing LED typically indicates a communication issue.
Possible causes:
- Incorrect NMEA 2000® network termination.
- Missing network device.
- Network communication fault.
Check:
- NMEA 2000® backbone termination resistors.
- Network connections.
- Presence of other active NMEA 2000® devices.
Normal Operating LED Patterns #
The sender will indicate normal operation based on the configured measurement mode.
Level Mode #
LED flashes:
Once every 2.5 seconds
The sender is operating normally and reporting tank level information.
Volume Mode #
LED flashes:
Twice every 2.5 seconds
The sender is operating normally and reporting calculated tank volume information.
Inaccurate Tank Level Readings #
If fuel or water level readings are incorrect:
Inspect the following:
Verify End Cap Installation #
Confirm:
- Sender end cap is installed correctly.
- End cap is secure.
- No mechanical damage is present.
A missing or improperly installed end cap can affect sender accuracy.
Clean Sender Rods #
Contamination on the sender rods may affect readings.
Recommended procedure:
- Remove the sender as required.
- Carefully clean the sender rods.
- Inspect for buildup or contamination.
- Reinstall sender.
- Perform calibration procedure.
Recalibrate Sender #
After cleaning or correcting installation issues, recalibrate the sender using the standard Offshore Systems UK calibration procedure.
Red LED Fault Condition #
A red LED indicates a detected short circuit.
Possible causes:
- Damaged sender sleeve.
- Improperly fitted end cap.
- Mechanical damage to the sender assembly.
Recommended actions:
- Inspect the sender physically.
- Check the end cap fitment.
- Inspect the sleeve for damage.
- Correct the issue before replacing the sender.
The red LED will remain active while the short condition exists.
Quick Diagnostic Summary #
| Symptom | Most Likely Cause | Action |
| No LED activity | Power or configuration issue | Verify network power and Tank Type setting |
| Rapid flashing | NMEA 2000® communication issue | Check termination and network devices |
| One flash every 2.5 seconds | Normal Level Mode operation | No action required |
| Two flashes every 2.5 seconds | Normal Volume Mode operation | No action required |
| Incorrect readings | Dirty rods, calibration, end cap issue | Clean and recalibrate |
| Red LED | Short circuit | Inspect sender components |
Owner Tip #
The diagnostic LED is the fastest way to determine whether a fuel or water sender issue is related to the sender itself, vessel network communication, or calibration. Always perform LED diagnostics before removing or replacing the sender.
This guide is intended as a supplemental Ocean Alexander reference and does not replace the official Offshore Systems UK technical documentation.
East Coast Yacht Group
2955 West State Road 84
Fort Lauderdale, FL 33312
Service Department
954.530.2033
Contact our Service Department today to learn how we can help ensure safe and peak performance for your vessel.
