20 Most Recent Garmin Fishfinder 90 Questions & Answers

Question: What are the extra wires used for on the power cable for my fishfinder? I found this on the carmin website under questions and answers. I think your cable is ok to use according to this. --> Answer: Not all of the wires in the harness are required for use. To connect the unit to the power source, only the black & red wires are required (black to ground, red to positive). Here are descriptions of the other wires in the harness:

• The Blue wire is used for a NMEA data out connection to another NMEA compatible device. The fish finder outputs NMEA 0183 version 3.01. The receiving device must be compatible with this format and looking for the NEMA sentences DPT, DBT, MTM, or VHW.
• The Brown wire is used for a NMEA data in connection to receive data from another NMEA compatible device.
• The Yellow wire is used to connect to an external buzzer or alarm to alert you to any alarms which have been set to sound on the device. The Yellow GARMIN wire connects to the negative end of the external alarm. The positive return on the alarm will connect to the red positive wire of GARMIN.
• The green, white, and any other colors present have no connection purpose related to your fishfinder. The 18 Pin connector wiring harness is used by several other devices which utilize these wires.

If the device is only being connected to power & do not require a NMEA interface, PC connection, or external alarm support, only the red & black wires are required.

This indicactes the sonar sensor unit is malfunctioning or it's disconnected (or the cable connecting it is damaged). You will have to check it - ideally using another central unit. If the unit is damaged then you will have to either attempt at fixing it yourself by cutting the cable and the housing open, locating the fault and fixing it or just by replacing the entire system since you can't replace the sensor alone- it's not sold separately or available as a replacement part.
BTW sending it to be fixed is not an option, it would cost you over $150 which is well above what this unit sells for when new

I think the water you're working is a little shallow and that's why you're not getting the response you'd expect.

You can have the Depth Range as Auto which automatically tracks the bottom or set if anywhere between 5 and 600 feet.

You can also set the Scroll Speed as Ultra, Fast, Medium, Slow & Paused so it depends what the owner has it set to as to how quickly it will respond to movement.

Hello
More than likely the Sonar transducer has failed. Since Garmin doesn't release repair information to the public you will need to send it back to Garmin for repair or exchange, since the model is no longer sold they will most likely offer you a discount on a newer model of the 340C.. Here is a link to the out of warranty web page of Garmin.

http://www8.garmin.com/support/outofwarranty.html

Check your battery voltage, this can occur with low voltage. Charging the battery often resolves this issue.

Looking at the plug connection on the back of the head display, with the index at 12:00: Positive is the pin at 8:00, negative pin is at 7:00 ...

You can find Garmin fishfinder manuals at InstructionSheets.com.

Go here to get your manual Garmin Fishfinder 90 manual.

possibly.most ive owned will flash random numbers when out of the water.the fact its flashing or reading numbers at all,means its working.youll have put it in water to see how accurate,obviously

All transducers should read 0 ohms or close to it. If not you most likely have a broken pin in the connector or wire.

I can't remember correct setup but make sure that box is powered and connected to GPS in right input. With no power to box it won't be discovered by head unit.