SECTION FOUR — Troubleshooting and servicing the
No echoes displayed when STAR key is pressed.
Contact Northstar Service to upgrade to the latest version of 961/962 software.
Configure NMEA Port 3 for the 491. See the “Initial checkout” section of this manual.
Is the
Advance YES Speed set to 
zero?
NO
Is the
961/962
NO software Version 3.0 or
greater?
YES
Has
NO NMEA Port 3 
been configured
for the 491?
YES
Change the Advance Speed setting.
1.Check fuses and circuit breakers
2. Check power to 491 with | OFF | Check | STEADY | ||
GREEN | |||||
a voltmeter. | |||||
| |||||
| the 491's STAT |
| |||
3. Verify that the data cable |
|
| |||
| indicator |
| |||
between the 961/962 and |
|
| |||
|
|
|
| ||
the 491 is properly wired |
|
|
|
| |
and connected. |
|
|
|
| |
| FLASHING | RED |
| ||
| GREEN |
|
| ||
The 491 and the 961/962 aren't communicating properly. Check the wiring of the data 
cable between the 961/962
and the 491.
491 is communicating with the navigator
1.Check transducer connector for the proper wiring.
2.If wiring is correct,check transducer impedance with an ohmmeter.
3.If the transducer is open or shorted, replace it
There's a hardware problem with the 491.
Figure 12: 961/962 echo sounder system troubleshooting
PAGE 22 | 491 INSTALLATION MANUAL Revision A |