Westerbeke 44A FOUR - 35C THREE Operator's Manual page 37

TACHOMETER
TACHOMETER/HOUR METER
The tachometer/hour meter used in propulsion engine instru-
ment panels contains two separate electrical circuits with a
common ground. One circuit operates the hour meter and the
other the tachometer. The hour meter 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 troubleshoot-
ing a fault in either of the two circuits in a tachometer/hour
meter.
Hour meter 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-
minal to alterna'or connection.
Tachometer Sticking
1.
Check for proper AC voltage between "tach inp." termi-
nal 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. Using a hand held strobe tachometer reading front crank
pulley speed. Adjust the speed to 1/2 rated engine rpm.
b. Using the coars adjustment, select A, B, 4, 6, or 8 that
puts the panel tachometer rpm reading the closest to the
strobe tachometers rpm reading.
c. Using a 5/64 (2mm) allen wrench, adjust the calibration
pod on the panel tachometer to read the same as the
strobe tachometer's rpm.
NOTE:
Current model tachometers use a coarse adjustment
dial to set the tachometer to the crankshaft
p~lley
rpms. The
calibrating screw is then used for fine tuning.
HT
IDLE SPEED ADJUSTMENT
& TACHOMETER CHECK (New Installation}
Checking the idle speed
NOTE:
In a new installation having new instrument panels,
the tachometer may not always be correctly calibrated to the
engines rpm. This calibration should be checked in all new
installations.
31
1.
Warm up the engine to normal operating temperature.
Remove any specks on the crankshaft pulley with a clean
cloth and place a piece of suitable reflecting tape on the
pulley to facilitate use of a photoelectric type tachometer.
2. Start and idle the engine.
3.
Aim
the light of the tachometer onto the reflecting tape to
confirm the engine speed. Check the instrument panel
tachometer reading. Adjust the tachometer in the panel by
using the instrument coarse adjustment to calibrate the
instrument reading to the closest R.P.M. that the photo tach
is showing. Then use the fine calibration adjustment to
bring the instrument to the exact reading as the photo tach.
4. Adjust the idle speed
if
the engine speed is not within the
specified value.
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