Troubleshooting Seatalk1 (ST1) Network Problems – Complete Guide

Discover common causes of ST1 communication failures and learn step-by-step how to diagnose and fix problems with the Seatalk1 network.

If nothing has recently changed in the system, there are two common causes of ST1 network problems:

• Cable or connection failure (e.g., ST1 data cable shorted to 12V or 0V)
• A faulty or unpowered product that is bringing down the ST1 network and preventing communication

Diagnostic Steps for ST1 Network

1. Check that all devices are powered on.
   Older ST1 devices (older than ST60+, ST6002/7002/8002, SPX autopilot course computers) can lock the network. Blown fuses or switched-off circuit breakers can cause the problem.
2. Simplify the network and start with two devices that can communicate.
   Build a functioning core network and add devices incrementally to identify the source of the error.

Requirements for Troubleshooting

• At least 3 ST1 devices
• At least 2 transmitters (e.g., autopilot course computer, GPS, speed instrument)
• At least 2 receivers (e.g., autopilot display, chartplotter)
• Cables to change connections

Start by connecting a transmitter and a receiver that can display data from the transmitter. If communication fails, replace devices or cables until you find a working combination. Once two devices are working, add more devices one at a time until the problem occurs.

Advanced Troubleshooting

The best tool is an oscilloscope. A multimeter is not sufficient because network traffic is too fast. Look for a 0V–12V square wave at 4800bps. Examples of a healthy ST1 network:

Examples of networks with faulty communication chips:

If you cannot solve the problem yourself, hire a service technician with an oscilloscope and test equipment.

ST1 Cable Colors