Installing The Wiring Harness; Connecting The Wiring Harness To Power - Garmin GPSMAP 420 Installation Instructions Manual

Installing the Wiring Harness

The chartplotter comes with a wiring harness that connects the chartplotter to power and to optional NMEA 0183 and Garmin CANet devices.
If applicable, the wiring harness also connects the chartplotter to a transducer.
The wiring harness does not connect to a NMEA 2000 network. For instructions on connecting to a NMEA 2000 network with compatible
devices, see page 8.
To the GPSMAP 400/500
series chartplotter
Notes:
• Use an AGC/ 3AG - 3 Amp replacement fuse.
• If it is necessary to extend the power and ground wires, use 22 AWG wire.
• You can wire the harness directly to the battery, or if your boat has an electrical system, you might be able to wire the harness to an
unused holder on the fuse block. If you use the boat fuse block, remove the in-line fuse holder on the power wire of the harness.
• Do not cut the transducer cable, because this voids your warranty.
NotIce: The maximum input voltage is 32 Vdc*. Do not exceed this voltage because this can damage the chartplotter and void the warranty.
NOTE: During a typical installation, use only the red and black wires. The other wires do not have to be connected for normal operation of the
chartplotter. For information on connecting to a NMEA 0183- or Garmin CANet-compatible device, see

Connecting the Wiring Harness to Power

1. Use a test light or voltmeter to determine the polarity of the voltage source.
2. Connect the red (+ or positive) wire to the positive voltage terminal. (If you use the
fuse block on the boat, route the positive connection through the fuse, as shown on the
diagram.)
3. Connect the black (- or ground) wire to the negative voltage terminal.
4. Install or check the 3 A fuse (in the in-line fuse holder, or on the fuse block of the boat).
* Certain GPSMAP 400/500 series chartplotters can be connected to higher-voltage power sources. Refer to the * Certain GPSMAP 400/500 series chartplotters can be connected to higher-voltage power sources. Refer to the
Power section of the System Specifications on Power section of the System Specifications on

GPSMAP 400/500 Series Wiring Harness
page 10 page 10 for more information. for more information.
Wire Color Wire Function
Red Power (10– Vdc*)
Ground
(power and NMEA 018)
Black
NMEA 018 port 1 Tx (out)
Blue
NMEA 018 port 1 Rx (in)
Brown
NMEA 018 port  Tx (out)
Grey
NMEA 018 port  Rx (in)
Violet
Green CANet L (if applicable)
White CANet H (if applicable)
Orange Accessory on
Yellow Alarm low
To transducer (if applicable)
page 8.
 A fuse  A fuse
Boat ground Boat ground
— —
+ +
To device To device
GPSMAP 400/500 Series Installation Instructions
To 10– Vdc* boat supply To 10– Vdc* boat supply
2A 3A 2A 3A
Fuse Block Example Fuse Block Example