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CHECKSUM EVALUATION
During testing it was discovered that
some Navigation Devices incorrectly
calculate the checksum, causing the
checksum error message to be displayed
repeatedly.
The checksum evaluation can be turned
off by turning the master select switch to
STANDBY and press the ADJUST key
repeatedly until 'cn:ON' is displayed.
Press either the up or down ARROW key
until 'cn:OF' is displayed.
The RMA, RMB and RMC data
sentences contain a 'checksum' which is
determined by the contents of the
sentence. The autopilot can calculate
what the checksum should be and
compare it to the sentence. If the
sentence was received correctly , the two
checksums should be the same. If they
are different the autopilot assumes that
the sentence was incorrectly received and
displays 'cn:Er'.
**** IMPORTANT ****
If you have installed a ComNav Marine reversing motor pump, a constant running pump or
an engine driven pump, there are several checks that must be done during the first several
weeks of usage in order to prevent poor or dangerous steering performance. During this
period you must check for air or leaks in your hydraulic system.
Residual air in your steering system
Following the initial installation and bleeding of your ComNav pump, some residual air may
remain suspended in the hydraulic fluid. During the first few weeks, this air will gradually
bleed out through the header tank or the highest helm pump and the oil level may go down.
Check several times and add more oil as required.
Leaking fittings or equipment
Following the initial installation and bleeding of your ComNav pump continuously monitor
the oil level of the reservoir or the highest helm pump in your steering system and add oil
as required. If this condition persists, it may be an indication of leakage in your steering
system. Check all hydraulic steering fittings and equipment for leakage.
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