Westerbeke W-70GA Installationshandbuch PDF herunterladen (Seite 34)

TACHOMETER

TACHOMETER/HOUR

METER

The tachometerlhour 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

the instrument.

The tachometer circuit operates on AC voltage 6-8 volts, fed

fTom

one

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

either

the two circuits in a tachometerlhour

meter.

Hour

meter

Inoperative

Check for the proper

voltage between (+) and

(-)

terminals.

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

voltage between tachometer input

terminal and

(-)

terminal with the engine running.

Voltage present - attempt adjusting meter through calibra-

tion access hole. No results, repair or replace meter.

AC voltage not present - check for proper alternator DC

output voltage.

3. Check for

voltage at tach terminal on alternator

ground.

4. Check electrical connections from tachometer input ter-

minal

alternator connection.

Tachometer

Sticking

Check for proper

voltage between "tach inp." termi-

nal and

(-)

terminal.

Check for good ground connection between meter (-)

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

the crankshaft

pulley retaining nut or with a strobe-type tach, read the

front crankshaft pulley rpm at idle.

h. Adjust the tachometer with a small Phillips type screw-

driver through the calibration access hole in the rear

the tachometer. Zero the tach and bling it

the rpm

indicated

the strobe or hand tach.

VerifY

the rpm at

idle and at high speed.

NOTE:

Current model tachometers use a coarse adjustmei1t

dial to set the tachometer to the crankshaft pulley rpms. The

calibrating screw is then used

for

fine tuning.

COARSE

ADJUSTMENT

INP

VOLTAGE

CALIBRATION

TACHOMETER

CALIBRATION

WIRE

TERMINAL

IDLE

SPEED

ADJUSTMENT

(New

Installation)

NOTE:

In a new installation (commissioning) the tachometer

in the instrument panel will not always be correctly

calibrated to the engine's RPM. The tachometers calibration

must be checked in a new installation (commissioning)

Place a piece

reflective tape on the outer edge

the

front crankshaft pulley.

Start the engine and allow the engine

warm up and

then set the engine speed at a high idle

1500 rpm, using

a strobe type tachometer shooting the front crankshaft

pulleys reflective tape for an accurate engine rpm reading.

3. Positive

the"coarse" adjustment at each

the six

selections.

Select the one that sets the tachometer reading

closest

the 1500 rpm.

4. Using a small phillips screw driver, adjust the calibration

pod

set the tachometer exactly on 1500 rpm.

Check the tachometer readings at idle and at high rpm.

6. Adjust the idle speed at a comfortable rpm, but not at too

Iowa

speed to induce vibration and stalling when shifting

the transmission.

Engines & Generators

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