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Northstar Explorer 435/438 Installation and Operation Manual 29
3. The fishfinder operates erratically:
a) Check that the transducer does not have
debris (e.g. weed, plastic bag) caught
around it.
b) The transducer may have been damaged
during launching, running aground or while
underway with debris etc. If the transducer
has been impacted, it may have been kicked
up on the bracket. If it is not physically
damaged, reset the transducer back to its
original position. (See the Transom Transducer
Installation Guide.)
c) When the transducer is less that 2 ft (0.6 m)
from the bottom, the depth readings may
become inconsistent and erratic.
d) Manual Gain may be set too low, which may
cause weak bottom echo or no fish signals. If in
Manual Gain, try increasing the Gain.
e) Ensure the back of the bottom surface of the
transducer is slightly lower than the front and
the front is as deep in the water as possible
in order to minimize the generation of
bubbles through cavitation. (See the Transom
Transducers Installation Guide.)
f) Check the transducer and power cable
connectors at the back of the display unit
are securely plugged in and the collars are
locked in place. The collars must be secure for
watertight connection.
g) Inspect the power cable from end to end for
damage such as cuts, breaks, squashed or
trapped sections.
h) Ensure there is not another fishfinder or
depth sounder turned on, which may
interfere with this fishfinder.
i) Electrical noise from the boat’s engine or
an accessory may be interfering with the
transducer(s) and/or the Northstar fishfinder.
This may cause the fishfinder to automatically
decrease the Gain unless using Manual Gain.
The fishfinder thus eliminates weaker signals
such as fish or even the bottom from the
display. This may be checked by switching
off other instruments, accessories (e.g. bilge
pump) and the motor until the offending
device is located. To stop problems from
electrical noise, try:
- re-routing the power and transducer cable(s)
away from the boat’s other electrical wiring.
- routing the display unit’s power cable directly to
the battery with an in-line fuse.
4. Bottom is not displayed:
a) The fishfinder may have Manual Range
selected and the depth may be outside the
range value selected. Either change the
fishfinder to Auto Range or select another
depth range (see section 4-4 Range).
b) The depth may be outside the fishfinder’s
range. While in Auto Range, the display unit will
display “--.-” to indicate that there is no bottom
detected. A display of the bottom should
reappear when in shallower water.
5. The bottom is displayed too far up
the screen:
The fishfinder may have Manual Range
selected and the selected Range value is
too high for the depth. Either change the
fishfinder to Auto Range or select another
depth range (see section 4-4 Range).
6. Bottom echo disappears or erratic digital
reading while the boat is moving:
a) Ensure the back of the bottom surface of
the transducer is slightly lower than the
front and the front is as deep in the water as
possible in order to minimise the generation
of bubbles through cavitation. (See the
Transom Transducers Installation Guide, for
more information.)
b) The transducer may be in turbulent water.
Air bubbles in the water disrupt the echoes
returned, interfering with the fishfinder’s
ability to find the bottom or other targets.
This often happens when the boat is
reversed. The transducer must be mounted
in a smooth flow of water in order for the
fishfinder to work at all boat speeds.
c) Electrical noise from the boat’s motor
can interfere with the fishfinder. Try some
suppression spark plugs.
7. If the fishfinder beeps when turned on but
nothing is displayed:
The fishfinder may be operating, but the
backlight settings may have been set too low.
See section 2 Basic Operation, to adjust the
fishfinder backlight. (Press
twice)
8. The wrong language is displayed:
See section 3-1 Setup > System.