Control Panel Troubleshooting - Westerbeke 90A Four Service Manual

CONTROL PANEL TROUBLESHOOTING
TACHOMETER/HOURMETER
The tachometer/hourmeter used in propulsion engine instru-
ment panels contains two separate electrical circuits with a
common ground. One circuit operates the hourmeter and the
other the tachometer. The hpurmeter circuit operates on
12
volts alternator charging voltage supplied to the ( +) terminal
on
the
back of the instrument
The tachometer circuit operates on AC voltage 6-8 volts, fed
from one of
the
diodes in the alternator and supplied to the
tachometer input terminal while the engine is running, and
the alternator producing battery charging voltage 13.0-14.8
volts DC.
The following
are
procedures to follow when troubleshooting
a fault in either of the two circuits in a tachometer/hour-
meter.
Hourmeter Inoperative
·Check for the proper DC voltage between (
+)
and (-)
terminals.
1. Voltage present - meter is defective - repair or replace.
2. Voltage not present - trace (
+)
and (-) electrical
con-
nections for fault. (Jump 12 volts DC to meter(+)
terminal to verify
the
operation.)
Tachometer Inoperative
Check for the proper AC voltage between tachometer input
terminal and (-) terminal With the engine running.
1. Voltage present - attempt adjusting meter through calibra-
tion access hole. No results, repair or replace meter.
2. AC voltage not present - check for proper alternator DC
output voltage.
3. Check for AC voltage at tach terminal
on
alternator to
ground.
4. Check electrical connections from tachometer input ter-
IJl.inal to alternator connection.
Tachometer Sticking
1. Check for proper AC voltage between ''tach inp." terminal
and (-) terminal.
2. Check for good ground connection between meter(-) ter-
minal and alternator.
3. Check that alternator is well grounded to engine block at
alternator pivot bolt.
Tachometer Inaccurate
a.
With a hand-held tach
on
the front of the crankshaft
pulley retaining nut or with a strobe-type
tach,
read the
front crankshaft pulley
rpm
at idle.
b. Adjust
the
tachometer with a small Phillips type screw-
driver through the calibration access hole in the
rear
of
the tachometer. Zero the tach and
bring
it to the
rpm
indicated by the strobe or hand tach. (Verify the rpm at
idle and at
high
speed 3000-3600 rpm). (Adjust the tach
as needed.)
NOTE:
Current model tachometers use a coarse adjustment
dial to
set the tachometer to the crankshaft pulley rpms. The
calibrating screw is then used for fine tuning.
COARSE
ADJUSTMENT
~~-(+)TERMINAL
CALIBRATION TACHOMETER INPUT
CURRENT TACHOMETER
(AC VOLTAGE)
LIGHT
(-)GROUND
TERMINAL
(-} GROUND-z .
TERMINAL LIGHT
~
.
(+)TERMINAL
EARLY MODEL TACHOMETER
l'W'jWESTERBEICE
Engines & Generators
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