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5. The unit comes on before I press POWER, and won’t turn off.
Check the transducer cable—if the outer jacket of the cable has been cut and the
cable is in contact with bare metal, you need to repair the cut with electrical tape.
If there is no problem with the cable, disconnect the transducer from the unit and
see if the problem is corrected, to confirm the source of the problem.
6. I get gaps in the reading at high speeds.
Your transducer needs adjusting. If the transducer is transom-mounted, there are
two adjustments available to you—height, and running angle. Make small
adjustments and run the boat at high speeds to determine the effect. It may take
several tries to optimize high speed operation. This can also be a result of air or
turbulence in the transducer location caused by rivets, ribs, etc.
7. My unit loses power at high speeds.
Your 405SX has over-voltage protection that turns the unit off when input voltage
exceeds 20 VDC. Some outboard motors do not effectively regulate the power
output of the engine’s alternator and can produce voltage in excess of 20 volts
when running at high RPMs. The
405SX displays input voltage in the Diagnostic
screen. Use this readout to determine if the voltage exceeds 20 VDC.
8. The screen begins to fade out. Images are not as sharp as normal.
Check the input voltage using Diagnostic. The 405SX will not operate on input
voltages below 10 VDC.
9. The display shows many black dots at high speeds and high
sensitivity settings.
You are seeing noise or interference caused by one of several sources. Noise can
be caused by other electronic devices. Turn off any nearby electronics and see if
the problem goes away. Noise can also be caused by the engine. If engine noise
is causing the interference, the problem will intensify at higher RPMs. Increase the
engine speed with the boat stationary to isolate this cause. Propeller cavitation
can appear as noise on-screen. If the transducer is mounted too close to the
propeller, the turbulence generated can interfere with the sonar signal. Ensure
that the transducer is mounted at least 38cm (15") from the prop.
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