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TESTING THE
ALTERNATOR AND VOLTAGE REGULATOR
GENERAL
Fixed clamps should be used for all testing of the
alternator
equipment.
So-called
crocodile clamps
should not be
used
as they have a certain
I
t endency to
loosen.
A
loose lead
can result in the alternator and
regulator being damaged. When about to connect up
instruments, disconnect the battery first.
CHECKING THE ALTERNATOR CIRC UIT
Before carrying out any tests on the alternator
or
regulator in the vehicle check the battery and vehicle
wiring system for damaged
lead
s
or insulation, loose
or conroded lead telrminals and poor ea'fthing.
Check
the fan
belt.
Any of the above faults must be re-
medied before the electrical
checks
can be
started.
TESTI N
G
TH
E
BA
TTERY
Test the
bottery with
a
hydrometer and
battery tester.
If
the
battery is not fully charged, remove it from
the
ear
and
charge it or
replace
if with a new one if ne-
cessary. A fully charged batf,ery which is otherwise in
good condition should always be used when testing.
CHECKING THE
VOLTAGE
DROP
This test is made to check the leads between the alter-
nator and the batf,ery and also the battery earth lead.
The test should be carried out with a fully charged
battery in good condition.
The
battery terminals should
be weil cleaned and tightened. Load
,
t he alt,ernator
with about
10
amps. Suitable loa,d: Mainbeam light
switched on. With
the
engine running and the alter-
nator supplying
10
am ps., measure with a suitable
voltmeter
the
voltage between the positive pole of
the
battery and B
+
on the
al,
t ernator.
If the voltage
at this test exceeds
0.3
volt,
there
must be a fault in
the lead or contact, which must be remedied imme-
diately. Af ter repairing the leads or contacts, measure
once aga in. With the same load as above, measure
the voltage drop between the negative pole of
the
battery and the alf.ernator terminal
D-.
Here
the
voltage drop must not exceed
0.2
volt. If the voltage
drop exceeds
0.2
volt, check the battery earth lead,
the alternator contact with the engine and
,
t he
engine
contact with the chassis. Af ter making
,
t he
necessary
repairs measure again.
CHECKING THE ALTERNATOR
(In
a test bench or in the vehicle)
Connect
up
the alternator as
shown
in Fig.
3-22.
Check
that the current through the field winding (ammeter
C)
is
3-3.5
amps.
(If
the current is not the correct one,
then check the brush holder and field winding.) Run
the alternator to a speed of
3000
r.p.m.
(Engin
e speed
1500
r.p.m.).
The
alternai
t or should then produce at
least
48
amps
at
14
volts. (A
further
load may be
connected
up in
order to maintain the voltage
at
14
volts.)
Th is
applies
to
a
warm
al,
t ernator and
an ambient
temperature of
25°
C
(77°
F).
Measure the voltage at B
+
and
61 when the
alternator
charges.
The
voltage
should
be
0.8-
0.9
volt more than at ter-
minal 61, O'therwise the isolation diodes must be faulty
and
shou
ld
be replaced.
CHECKING THE VOLTAGE REGULATOR
(Ir.
a test bench or in
the
vehicle)
Connect
up the alternator and
regulator
as shown
In
Fig.
3-23.
Run the
a.lternator
at about a speed of
5000
r.p.m. (engine
speed
25000
r.p.m.)
for
15
seconds.
Then
read off the voltage on the
voltmeter.
With no load
on the
alterna'
t or, the voltmeter
should read
13.1-14.4
volts with the r,egulator ambient temperature at
25°
C
(77°
F).
+-
VO
LVO
103054
Fig. 3·22.
Wiring diagram for testing
alternator
A Alternotor
B
Battery 60 Ah
C Ammeter 0-10 amps
.
D Ammeter O-50 amps.
E
Voltmeter 0-20
volts
3:9
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