Humminbird 343c Display Problems, Finding the Cause of Noise, Problem Possible Cause, Isolation

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Display Problems

There are several main conditions or sources of possible interference that may cause problems with the quality of the information displayed on the control head. Look in the following table for some symptoms of display problems and possible solutions:

Problem

Possible Cause

Finding the Cause of Noise

Electrical noise usually affects the display with many black dots at high speeds, and high sensitivity readings. One or more of the following sources can cause noise or interference:

Possible Source of Noise

Isolation

The control head loses power at high speeds.

When the boat moves at higher speeds, the bottom disappears or suddenly weakens, or the display contains gaps.

There are no fish detected, even when you know they are in the water under the boat, or sonar readings seem weak or faulty.

If the power output of your boat’s engine is unregulated, the control head may be protecting itself using its over-voltage protection feature. Make sure the input voltage does not exceed 20 Volts.

The transducer position may need to be adjusted. A mix of air and water flowing around the transducer (cavitation) may be interfering with the inter- pretation of sonar data. See your Installation Guide for suggestions on adjusting the transducer position.

Electrical noise from the boat’s engine may be interfering with sonar reception. See Finding the Cause of Noise for more information.

Sonar readings may be affected if the transducer is not positioned correctly (i.e. mounted at an angle, not straight down), or there is some kind of mechanical interference, either because it is mounted inside a hull that is too thick for proper sonar transmission, the bond between the transducer and the hull is not airtight, or because the transducer is dirty. Check with your Installation Guide for guidance on re-positioning the transducer, and make sure the transducer is clean.

Low battery voltage may be affecting the power of signal transmission.

Electrical noise from the boat’s engine may be interfering with sonar reception. See Finding the Cause of Noise for more information.

Other electronic devices

Turn off any nearby electronic devices to see if the

 

problem goes away, then turn them on one at a

 

time to see if the noise re-appears.

The boat’s engine

To determine whether the boat’s engine is the

 

source of the noise, increase the RPMs while the

 

boat is in neutral and stationary to see if the noise

 

increases proportionately; if noise appears when

 

you rev the engine, the problem could be the spark

 

plugs, alternator, or tachometer wiring. Replace the

 

spark plugs with resistor plugs, install an alternator

 

filter, or route the control head power and

 

transducer cables away from the engine wiring.

Cavitation from the boat’s

Turbulence created by the propeller can cause

propeller

noise; make sure the transducer is mounted at least

 

15” (38 cm) from the propeller, and that the water

 

flows smoothly over the face of the transducer at

 

all times.

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Contents 343c Operations Manual Table of Contents Thank YouTroubleshooting Alarms Menu TabSetup Menu Tab Specifications Glossary Contact HumminbirdHow Sonar Works DualBeam Plus Sonar What’s On the Display High Sonar Intensity Return Bait BallViews Sonar ViewUnderstanding Sonar History Real Time Sonar RTS WindowFreeze Frame Bottom Presentation Sonar Zoom View 200/83 kHz Split Sonar ViewKey Functions POWER/LIGHT KeyBig Digits View Circular Flasher ViewMenu Key WAY Cursor Control KeyExit Key Powering Up the Unit Menu SystemNormal Operation Exit Normal operation by powering your Fishing System offStart-Up Options Menu Normal Simulator System StatusExit System Status by powering your Fishing System off Self Test Accessory TestExit the Simulator by powering your Fishing System off SimulatorSensitivity To adjust the SensitivitySonar X-PressTMMenu Highlight Sensitivity on the Sonar X-PressTMMenuUpper Range To adjust the Upper RangeTo adjust the Lower Range Lower RangeBottom Lock Chart SpeedZoom Level Bottom RangeTo use Beam Select Sonar Menu TabBeam Select Highlight Beam Select on the Sonar main menuFish ID+TM To change the Fish ID Sensitivity settingTo change the RTS Window setting Fish ID SensitivityKHz Sensitivity Bottom ViewZoom Width Depth LinesSurface Clutter Noise FilterMax Depth Alarms Menu Tab To change the Water Type settingWater Type Low Battery Alarm Depth AlarmFish ID Alarm Temp AlarmTo change the Alarm Tone setting Alarm ToneSetup Menu Tab Highlight Alarm Tone on the Alarms main menuUnits Temp User ModeUnits Depth Units DistanceTriplog Reset Restore DefaultsSelect Views Select Readouts Depth OffsetTemp Offset Troubleshooting To change the Speed Calibration settingSpeed Calibration Finding the Cause of Noise Display ProblemsProblem Possible Cause IsolationSpecifications GlossarySonar Terms 531447-1A343cEng.qxd 11/11/2005 918 PM 531447-1A343cEng.qxd 11/11/2005 918 PM Receiver See Transmitter 531447-1A343cEng.qxd 11/11/2005 918 PM Contact Humminbird