SERVICE MANUAL
ohmmeter, check between points A and
D (Fig.
104)
and then reverse the ohm
meter lead connections. If diode trio is
good, it will give one high and one low
reading. If both readings are the same,
the diode trio is defective. Repeat this
test at points B and D and at C and D.
The rectifier bridge (Fig.
105)
has a
grounded heat sink (A) and an insulated
heat sink
(E)
that is connected to the out
put terminal. Connect ohmmeter to the
grounded heat sink (A) and to the nat
metal strip (B). Then reverse the ohm
meter lead connections. If both readings
are the same, the rectifier bl"idge
is
defec
tive. Repeat this test between points A
and C, A and D, B and
E,
C and
E,
and
D and
E.
Capacitor
(11
-
F
ig
.
101)
con
nects to the rectifier bridge and grounds
to end frame, and p'rotects the diodes
from voltage surges.
Test the stator windings for grounded
or open circuits as follows: Connect ohm
meter leads successively between each
pair of leads. A high reading would in
dicate an open
circuit.
The three stator
leads have a common connection in ihe
center of the windings. Connect ohm
meter leads between each stator lead
and stator frame. A very low reading
would indicate a grounded circuit. A
short circuit within the stator windings
cannot be readily determined by test
because of the low resistance of the
windings.
Brushes and springs are available on
ly as an assembly which includes brush
holder
(1
4
-
F
ig
.
101).
If brushes are re
used, make sure all grease is removed
from surface of brushes before unit is
reassembled. When reassembling, first
install regulator and then brush holder,
springs and brushes. Push brushes up
against spring pressure and insert a
short piece of straight wire through hole
in brush holder and through end frame
to outside. Be sure that the two screws
I
8
0
I
c
Fig. 104-Diode trio test points, refer to text.
at points A and B (Fig.
103)
have in
sulating washers and sleeves.
NOTE: A
ground
at
these
points will
cause
no output, or uncontrolled
o
ut
p
u
t
.
Remove and inspect ball bearing
(6-Fig.
101).
If bearing is in satisfactory
condition, fill bearing
JA
full with Delco
Remy Lubricant No.
1948791
and
reinstall. Inspect needle bearing
(17)
in
slip ring end frame. This bearing should
be renewed if its lubricant supply is ex
hausted; no attempt should be made to
relubricate and reuse the bearing. Press
old bearing out toward inside and press
new bearing in from outside until nush
with outside of end frame. Saturate felt
seal with
SAE
20
oil and install seal.
Reassemble alternator by reversing
the disassembly procedure. Remove wire
retaining the brushes after end frames
are bolted together. Tighten pulley nut
to a torque of
68
N
·
m
(50
ft.-lbs.).
Models MF240-MF250 With
Lucas
Alternator
103.
TESTING. 'lb
check alternator
wiring harness continuity, disconnect
wiring connections from alternator and
turn start switch to auxiliary position.
Connect a voltmeter between ground
and each of the disconnected leads. Bat
tery voltage should be present at the
alternator
"+"
(battery) lead and the
"IND" (warning light) lead. A zero
Fig. 1 05-Brldge rectifier test points, refer to text.
Fig. 106-Connect test am·
meter and voltmeter as
shown to check alternator
output on Models MF240 and
MF250 equipped with Lucas
alternator.
Paragraphs
1 03-1 04
reading indicates open circuit in wiring
or faulty warning light bulb. If an addi
tional ground lead is used on alternator,
check continuity of lead using an
ohmmeter.
If voltage is present at"+" and "IND"
leads, but warning light fails to come on
when leads are reconnected to alter
nator, a faulty regulator and/or field
(rotor) winding
is
indicated.
To
check alternator output, first
disconnect battery ground cable. Discon
nect wiring from alternator, remove
cover from rear of alterna
t
or, then recon
nect wiring leads. Connect an ammeter
between starter solenoid te1minal and
alternator output terminal (Fig.
106).
Connect a voltmeter between output ter
minal and ground. Connect a carbon pile
across battery terminals. Reconnect. bat
tery ground cable and
start
engine.
Operate engine at
2000
rpm, turn on
headlights and adjust carbon pile as
re
quired to obtain maximum current out
put. Ammeter reading should be
approximately
34
amperes. Adjust car
bon pile
so
ammeter reading is less than
10
amperes. Voltmeter reading should be
within range of
13.6-14.4
volts.
If output is low,
use
a jumper lead to
short together the
"F"
and "-" connec
tions (Fig.
106)
on alternator. If output
is now within specified range, a faulty
regulator and/or field winding
is
in
dicated. If output is still low, fault is
elsewhere in alternator. Disassemble
and
check
as outlined in paragraph
104.
104.
OVERHAUL. 'lb
disassemble
alternator, first remove rear cover
(17
-
F
ig
.
107).
Disconnect and remove
surge protection diode, regulator
(16)
and
brush holder
(13)
with brushes
(12).
Note
that these parts can be removed without
removing the alternator from the engine.
Any further disassembly of alternator
will require removal of alternator.
Scribe match marks on slip ring hous
ing
(11),
stator fi·ame
(10)
and drive end
frame
(3)
to ensure correct alignment for
reassembly. Unsolder sta
t
o
r
wires from
43