User's Guide

2110059 Rev 1.1 Proprietary and Confidential Page 73
9. Troubleshooting
9.1. Introduction
Some solutions to common problems are described here. They are grouped along the lines of the
four operations chapters. General problems communicating with the modem in the first section
and issues which are specific to particular modes in subsequent sections.
An up to date troubleshooting guide will be available on the Sierra Wireless Internet site at
www.sierrawireless.com.
If you cannot resolve a problem after reading this chapter and consulting our web site, please
contact the Sierra Wireless help desk at [phone] (between 06:00 and 17:00 Pacific Time)
or e-mail us at
[e-mail].
9.2. General Modem Problems
The SB300 Series modems are thoroughly inspected during manufacture. There are no end-user
access items within the case or on the circuit boards of the modem. If problems occur, check the
following:
Problem Description Suggestions
WirelessExpert fails to setup
Windows Dial-up
Networking Connection
Watcher fails to locate the
modem.
Use the Windows Start > Settings > Control Panel > Modems to
install the Sierra Wireless modem.
Modem fails when
transmitting.
The LED indicator
(SB300/320) does not light.
Check that the power source has adequate voltage and current. The
modem requires regulated 5 Vdc at 850 mA. If the power is marginal it
can be the problem. The SB300 Series modems draw up to 850 mA
under maximum power output. The power output is a function of the
modem’s distance from the Mobile Data Base Station. It is possible for
the modem to work well with a particular power supply in a location
requiring low power output (low current draw), and yet to fail using the
same power supply in a location requiring a high power output.
Check the amperage rating of the power supply to verify that it is
adequate for all situations.
Check the fuse (if any) in the power source and as a final test use a
voltmeter to check for an open cable.
Modem disconnects or resets
intermittently.
Ensure the DTR signal is not floating or being changed by the host.
Set AT&D0 to have the modem ignore DTR.
Verify that CSC radio signal strength is sufficient. Weak signals may
cause loss of carrier and subsequent disconnection. Use higher values
in register S10 (Lost Carrier Hang-up Delay).
AT commands are sent to
configure the modem but the
modem does not use the
settings when running an
application.
Verify that the application does not send its own modem setup
commands after you have configured the modem. If it does, then either
disable the feature or set your configuration in the application’s setup
string.