Yanmar 1GM User Manual page 204

198
gear as it rotates. The sensor sends the resulting electrical
signal to the tachometer, which converts it into indicator
needle movement.
NOTE
While the sensors for all engines are inter-
changeable. the tachometers are not. Due to
the difference in number ofring gear teeth.
the tachometer used on 3N..., and 3HM35
engines is nol
interchangeable with other
engines.
Before troubleshooting the tachometer, check for faulty
connections, then recheck tachometer operation. If the
problem rema ins. refe r to the follow ing sec tions.
CH APTE R NINE
Tachometer Sender
To check the tachometer sender, proceed as follows:
1. Disconnect the leads from the sende r ( Figu re 29).
2. With the engine stopped. use an ohmmeter to check the
resistance between the sender leoninaIs. Resistance
should be 1500-1700 ohms.
3. Run the engine. Measure the alternating current volt-
age between the sender terminals. The voltage reading
should be at least one volt.
4. If the sender fails either test, replace the sender.
Tac homet er Ga uge
To check the tachometer gauge unit, proceed as fol-
lows:
I. Disconnect the rcd'bleck and black wire leads from the
tachometer. With the key switch ON, measure the voltage
between the two wires. There should be 10-16 volts (bat-
tery voltage). If not, determine the ca use.
2. Disconnect the orange and blue/red wire leads from
the tachomete r. Run the engine. Measure the alternating
current voltage between the orange and blue/red wire
leads. The voltage reading should be at least one volt.
3. If the voltage reading in Step 2 is less than one volt,
check the wires and connections and check the sender as
described in the preced ing section.
..t. If the voltage readings in Steps I and 2 are satisfactory,
replace the tachometer.
M o del
lGM,lGM10
2GM,2GM20
3GM, 3GM30, 3HM
3HM35
Table 1 BATTERY CAPACITY (MINIMUMI
Voltage
12V
12V
12 V
12 V
Battery capacity
70 am p-hours
70 am p-hours
70 amp-hour s
100 amp-hours
T able 2 ALTERNATOR AND STARTER MOTOR TIGHTENING TORQUES
Mode l
lGM, lGM10,
2GM.2GM20,
3GM,3GM30
3HM,3HM35
Alternator mounting bolt
22-27 Nom
(16-20 ft.- lb .)
22-27 N.m
(16-20 ft .-lb.)
Starte r motor mounting bolts
45-50 Nom
(33-37 ft .-Ib,)
75-80 Nom
(55-59 ft.- lb.)