Where do all the wiring go to on the garmin 400c

mode then push unit then push reset to factory settings

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.

1) Disconnecting the nuvi from the charging cable.

2) Press and hold the battery meter icon for 8 seconds. This puts the nuvi into "system test" mode.

3) Plug in the power cable.

4) Click "Exit." The nuvi should now reboot, but remain in GPS mode!

The battery terminals are fairly easy to find which goes where. The PCB itself should have a + or - symbol depicting that black solders to (-) and red solders to (+)

Just so happens that my connector lost the red and purple wires, so the picture you have was a great help. Looking at the connector, the wire colors are red, purple, yellow, blue, black, green, brown.

I would do some Internet searches and type specs.

Is the transducer extending below the waterline?

Garmin Brown

The 3 wires are because the unit has a pcb on the battery which prevents over charging or shuts it off if the voltage falls too low. You can either use the pcb which is attached to the outside of the original battery (cut off the unit and reattach to the new battery with electrical tape) then solder the red and black wires to the appropriate Garmin wires or order a battery with built in pcb, If you do this, the green wire is not used, just solder the red and black wires from the plug-in connector to the new battery. It worked on my C330.

Lcstryper, I'm looking at my manual and you have it wired right, red power, black ground. Manuel also says to hold button down until you hear the power tone sound.

Got a meter, check to see you have power where you hooked it up.

Seadrive Joe