Service Manual

Alternator Output Tests
Keep the following points in mind when testing or
servicing the flywheel alternator.
CAUTION Operatlon with reversed positive (+)
and negative (-) battery connections or without
connection to
a battery wlll damage the voltage
regulator and/or the alternator stator.
1. Never reverse the battery leads.
2. Charging system tests require a fully charged
battery in good condition. Make sure the en-
gine is being run long enough and fast enough
in service to recharge the battery after each
start (engines with
12 VDC starters). Alternator
output is proportional to engine speed and ac-
cessories consume power otherwise available
for battery recharging.
3. The voltage regulator has built in protection
against open circuit and short circuit faults
)B+
terminal). It will not "turn on" under either condi-
tion or when battery discharge is extreme.
4. Check to see that the connections at the termi-
nals of the voltage regulator (three) or of the
rectifier bridge (four) are clean and tight.
5. Check to see that the wiring connected to the
B+ terminal (middle) of the voltage regulator or
to the
+ and terminals of the bridge rectifier
are not damaged, shorted or grounded.
6. To ensure a, good ground path to battery nega-
tive
(-), check to see that the voltage regulator
mounting surface is clean and that the screws
are tight.
6. Check to see that the positive and negative bat-
tery cables have good connections at the bat-
tery and engine and that they are not damaged.
After checking all of the above perform the following
tests
if there still is no alternator output when the en-
gine is running between
1800 and 3600 RPM. Refer
to Table
8-1 for test specifications. Use a multi-me-
ter (Simpson
270) when testing the alternator.
1. Check battery voltage when the engine is not
running. (Not applicable on recoil or
11 0 VAC
starter engines.)
If not within specifications
(Table
8-l), charge the battery before going to
Step
2.
2. With the engine running, check voltage regula-
tor output (DC voltage) at the battery terminals
or bridge rectifier output (DC voltage), as appli-
cable. Replace the
voltage regulator if output
is greater than specified.
If voltage regulator or
bridge' rectifier output is less than specified, go
to Step
3.
3. Disconnect the alternator stator leads from the
voltage regulator
or bridge rectifier and test for
alternator stator output (AC voltage) with the
engine running.
If stator output is less than
specified, go to Step
4. If stator output is as
specified but voltage regulator or bridge rectifi-
er output is
low, replace the voltage regulator or
bridge rectifier.
4. Shut down the engine and check for electrical
resistance between either alternator stator
lead and ground (bare engine metal) with an
ohmmeter. The meter should indicate infinite
resistance on its highest scale.
If resistance is
high, go to Step
5. If not, replace the stator.
5. Check alternator stator resistance by'connect-
ing an ohmmeter across the stator leads. Re-
place the alternator stator assembly
If stator re-
sistance on the lowest scale of the meter is ei-
ther higher or lowerthan specified. Replace the
flywheel assembly
if alternator stator resis-
tance
is as specified but alternator stator output
is less than specified. The probable cause is
loss of magnetism.