Troubleshooting - Navman F400 Installation And Operation Manual

The Fishfinder won't turn on:
1. Check the power cable socket at the back of the Fishfinder.
2. Make certain the power cable's red wire connects to the positive battery terminal
and the black wire to negative or ground.
3. Measure the voltage at the unit's power terminals. It should be at least 10 volts.
If it isn't:
•
•
•
4. Check any fuses you may have placed in the line.
The Fishfinder freezes, locks up, or operates erratically:
1. Electrical noise from the boat's engine or an accessory may be interfering with
the sonar unit.
To stop this, try:
•
•
2. Inspect the transducer cable for damage or pinched wires.
3. Check the transducer and power connector. Make certain it is securely plugged
into the unit.
Weak bottom echo, digital readings erratic, or no fish signals:
1. Make certain the transducer is pointing straight down.
2. Electrical noise from the boat's motor can interfere with the Fishfinder. This
causes the Fishfinder to automatically decrease the gain level unless the gain
control has been set manually. The Fishfinder thus eliminates weaker signals
such as fish or even the sea bed from the display.
3. Manual gain may be set too low, if you have the instrument set in manual mode.
4. The water may be deeper than the Fishfinder's ability to find the bottom. If it
cannot find the bottom return signal while it is in the automatic mode, the display
will flash continuously. It may change the range to a realistic one, and increase
the sensitivity. As you move into shallower water, a bottom signal should appear.
5. Check the battery voltage. If it is too low, the unit's transmitter power is also low,
reducing its ability to find the bottom or targets.
Bottom echo disappears or erratic digital reading while your boat is moving:
1. The transducer may be in turbulent water. Air bubbles in the water disrupt the
Fishfinder signals, interfering with its ability to find the bottom or other targets.
This often happens when you reverse the boat. The transducer must be mounted
in a smooth flow of water in order for the Fishfinder to work at all boat speeds.
2. Again, electrical noise from the boat's motor can interfere with the Fishfinder.
NAVMAN Fishfinder User Manual
the battery terminals or wiring on the terminals are corroded
the battery needs charging.
the wiring to the unit is defective
re-routing the power and transducer cables away from the other electrical
wiring on the boat
routing the unit's power cable directly to the battery instead of through a fuse
block or ignition switch
19