Sierra Wireless AirLink MP890, User Manual

Page: 37 / 67

Hardware and Software Installation
Rev 1.0 Mar.10 29
Figure 4-7: Wiring for the power harness.The white wire is the ignition sense.
• When the white ignition sense line is pulled high (5 to 36 V), the MP modem
powers on.
• When the ignition sense line is pulled low (less than 2 V), the MP modem
performs a controlled shutdown sequence (under software control), de-regis-
tering and saving any relevant operational data before powering off.
Ignition sense options
There are three ways to connect the ignition sense wiring:
• Engine on only. Connect the white ignition sense wire to the vehicle’s
ignition switch so that the MP modem is powered on only when the ignition
key is switched to the full “On” position, that is, when the engine has been
started. In this configuration,
the engine must be running for the MP modem
to be on.
—or—
• Accessory on. Connect the white ignition sense wire to the vehicle’s ignition
switch so that the MP modem is powered on when the ignition is switched to
“Accessory” mode. In this configuration, the MP modem is on
whenever other
vehicle electrical devices can be switched on —such as when the radio and
windshield fan can run.
—or—
Note: If you choose to
install a separate switch, it
must be connected to the
white ignition sense wire,
not the red battery wire, so
that the MP modem can
perform a controlled
shutdown, as described on
page 28 .
• Separately switched. Connect the white ignition sense wire to a separate
switch mounted in a convenient location, which allows the MP modem to be
turned on or off regardless of the position of the ignition key. In this configu-
ration, the MP modem can be powered on or off
even if the key is not in the
ignition.
The MP modem also has a “Power Off Timer”. When power is removed from the
ignition sense wire, the MP modem remains on for the period defined by the
Power Off Timer, up to a maximum of 240 minutes. The Power Off Timer is
configured in AceView. See the online help in AceView for details.
Black unfused wire
(Ground)
White wire
(Ignition sense)
Red wire
(Battery)
MP modem
5 A fuses (on red
and white only)
Switch (vehicle
ignition key, or
separate)
Vehicle battery