Sierra Wireless MP 875 User Manual
Page 34
MP875 Modem User Guide
34
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—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 32.
•
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
configuration, 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 3G Watcher. See the online help in 3G Watcher for details.
Ground the power harness
You must connect the black ground wire from the power
harness to the grounded negative terminal of the vehicle
battery, or another appropriate electrical ground. Failing to
ground the power harness properly may damage the MP
modem, may cause radio interference, and can be dangerous.
(See “Ground the MP modem” on page 28.) The ground wire
in the MP modem power harness is not fused.
Power connections
Connecting the MP modem’s power wires properly is
important—poor connections can damage the wiring, the MP
modem, or the vehicle’s electrical system, and can be
dangerous.
Note: Ensure that all wires are
correctly spliced or crimped.
Improper grounding and wire
connections may lead to
equipment damage or safety
hazards.
Correct wire splicing
You can splice the wires of the power harness to the car wiring.
Proper splicing is essential to reliable operation of the MP
modem. Do NOT use “quick taps”; they reduce the integrity of
the wire that is cut and let moisture into the cable.
An appropriate method of splicing is to strip a small portion of
the insulation, solder the wires together, then heat‐shrink the
connection to re‐insulate it.
Crimp terminals
If suitable terminal connection points are available on the
vehicle for power and ignition sense, then using automotive
crimp terminals is recommended. When using crimp
terminals, do not leave bare wire exposed. Do not use a crimp
terminal for more than one wire unless it is designed for that
purpose.