-,
..
'-'
SERVICE BULLETIN V.31
DATE:
1/23/85
BULLETIN
NUMBER:
148
MODEL:
ALL
PROPULSION
ENGINES
SUBJECT:
FIELD
TROUBLESHOOTING
TACHOMETER/HOURMETER
PN
11917
The
tachometer/hourmeter
used
in propulsion engine instrument panels contains
two
separate
electrical
circuits
with a
common
ground.
One
circuit
operates
the hourmeter,
and
the other the tachometer.
The
hourmeter
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 "tach
inp.1I
terminal while the
engine
,is
running,
and
the
alternator
producing battery charging voltage
13.0-14.8 volts
D.C.
'
The
following are procedures to follow
when
troubleshooting a
fault
in
either
of the
two
circuits
in the tachometer/hourmeter.
HOURMETER
FAULT
1. Inoperative
TACHOMETER
FAULT
1. Inoperative
PIN:
34791
CHECK
1.
Check
for proper
DC
voltage
between
(+)
and
(-)
terminals.
A.
Voltage present - meter defective - repair
or replace.
B.
Voltage
not
present - trace (+)
and
(-)
electrical
connections for
fault.
(Jump
12
Volts
DC
to meter (+) terminal to
verify operation.)
CHECK
1.
Check
for proper
AC
voltage
between
"Tach
Inp.1I
terminal
and,
(-)
terminal
with
engine running.
A.
Voltage present - attempt adjusting meter
through calibration access hole.
No
results,
repair or replace meter.
B.
AC
voltage not present -
check
for proper
alternator
D.C.
output voltage.
C.
Check
for
A.C.
voltage
at
tach terminal
on
alternator
to ground.
D.
Check
electrical
connectio'ns
from
"tach
Inp."
terminal to
alternator
connection.
J. H. WESTERBEKE CORP.
AVON
INDUSTRIAL
PARK,
AVON,
MASS.
02322·
(6f7}
5BB-7700
CABLE:
WESTCORP,
AVON·
TELEX:
92-4444
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