Honda GL1800 2004 Owner's Manual page 104

5. Route the auxiliary input patch cord through the hole in the bottom of the
fairing pocket.
6. Install the grommet B to left fairing pocket.
Do not pull on the auxiliary cord as the wires could be damaged.
grommet B
Some portable audio systems may pick up noise from the ignition.
Adjust the volume of the portable audio system so that it is about the same
level as the GL's radio volume. If the volume of the portable audio system is
set too high, the sound coming out from the speakers or headset may be
distorted.
Auxiliary Function
auxiliary input
patch cord
Audio Systems
97