Questions can be directed to Gary, Under (Contact Us) on the home
On the back of the alternator is the battery lead wire. Usually
a red insulator but not always, and on the SIDE of the case is a
place for a 2 wire plastic plug. The plug leads are parallel
with the edge of the case. IF you find an alternator with the 2
wire spades IN LINE with the fan, this is the older style
WITHOUT the internal regulator. Where this thing plugs in cast
on the case below the opening for the plug should be a number 1
and 2 below the respective terminals.
Wire #1 goes to the key switch
accessory terminal with a (10 ohm 10 watt) in line
you have an old style key switch that does not have an accessory
terminal you will need the Radio Shack part number 276-1661
diode to put in line with the #1 wire. It is installed with the
stripe towards the alternator. This will allow the car to stop
when your key is turned off)), this wire is HOT with the key in
the RUN position, BUT NOT THE START POSITION.
Wire #2 can be hooked directly
to the + battery wire on the back of the case, but should be
connected to the battery side of the starter solenoid if the
wire run is from one side of the car to the other. (This is
because if the alternator output is high there will be a
voltage drop of about 1 volt from the alternator to the battery
starter solenoid terminal and the rest of the car components
will not have the correct voltage during high charging rates).
Wire #2 is a sense voltage source for the regulator.
The idiot light is rather
unique. the light is a small dash lamp bulb on a special plug in
base. NORMAL lights require a ground and a hot wire. THIS LIGHT
IS NOT GROUNDED, instead both leads are insulated from the car
body. One side goes to the key switch, where it is fed 12 volts
when the key is ON, and the other goes to #1 on the alternator.
With the key ON and the engine not running, the light lights up,
as there is a voltage difference between the 2 leads. AS the
engine is running this wire has 12 volts across its entire
length and the lamp goes out, as BOTH LEADS have the same
voltage, when the alternator is charging. If the alternator
quits charging, then this wire loses its voltage and the light
comes one says I AIN'T WORKING, so you know something is wrong.
Usually on the GM's the battery wire off the back of the
alternator goes to the battery side terminal of the starter
solenoid. There is an in line fuse here most often on the
originals, consisting of a fusible link. Ditto for the
headlights and the rest of the cars wiring needs.
If you have an ammeter, make
certain that the STARTER DRAW IS NOT PUT ACROSS THE TERMINALS OF
THE AMMETER. The location of the ammeter can depend on what you
want to know. There are 2 places to put it, which I won't get to
here. A normal GM internal regulator alternator can have an
output from 45-70 amps depending on several variables. By
changing the internal windings and rotor it is possible to get
120-140 amps, but the life is shortened. You can also have a
self excited alternator, by changing the regulator and then you
have NO little wire plug to worry about, Just the big battery
wire. Speaking of which, this battery wire MUST BE 10 gauge
minimum and I like to solder the terminals on the end. I don't
trust crimp connections. If you have to run this wire a long
ways, then the wire MUST BE BIGGER. Delco manuals sometimes call
for #1 wire sizes for some alternators and 3/0 for some
starters, but you OUGHT TO SEE THE BATTERIES!!!
The following is a picture of
the wiring for the new alternator with old style key and new
style key with an example of the original wiring found in most
Studebaker Hawks or Larks. You will need to check your wiring
diagram to make sure the wiring is the same as that show in the
I know most are going to recommend the
one-wire GM setup but I prefer the Mopar unit. If you start with
the standard Stude V8 bracket on the exhaust manifold the front
lug of the Mopar alternator bolts to the front of the Stude
bracket and positions the belt alignment perfectly (assuming you
use a single groove pulley). A piece of angle iron with one hole
drilled in it is welded to the Stude bracket to make the support
for the rear lug of the alternator. The early Mopars ('61-'69)
used the same voltage regulator as the alternator equipped
Studies. It's a simple two wire hookup. The '70 and later used a
solid state regulator with three wires. The regulator can be
mounted in the same location as the original Stude and most of the
original wires used.
Alternator Model 10SI 61 amp. from 1984 chevy or 1971
The alternator illustrated in Figs. 1 and 2 features a solid state
regulator that is mounted inside the alternator slip ring end frame.
All regulator components are enclosed into a solid mold, and this
unit along with the brush holder assembly is attached to the slip
ring end frame. The regulator voltage setting never needs adjusting,
and no provision for adjustment is made.
The alternator rotor bearings contain a supply of lubricant
sufficiently adequate to eliminate the need for periodic
lubrication. Two brushes carry current through the two slip rings to
the field coil mounted on the rotor and under normal conditions will
provide long periods of attention-free service.
The stator windings are assembled on the inside of a laminated core
that forms part of the alternator frame. A rectifier bridge
connected to the stator windings contains six diodes and
electrically changes the stator A. C. voltages to a D. C. voltage
which appears at the alternator output terminal. Alternator field
current is supplied through a diode trio which also is connected to
the stator windings. A capacitor, or condenser, mounted in the end
frame protects the rectifier bridge and diode trio from high
voltages and suppresses radio noise.
No periodic adjustments or maintenance of any kind are required on
the entire alternator assembly.
A typical wiring diagram is illustrated in Fig. 3. The basic
operating principles are explained as follows. To excite or start
the alternator the switch is closed, current from the battery flows
through the ammeter and resistor (10 ohm 10 watt) to the
alternator No. 1 terminal, through resistor R1, diode Dl, and the
base emitter of transistor TR1 to ground, and then back to the
battery. This turns on transistor TR1 and current flows through the
alternator field coil and TR1 back to the battery.
With the alternator operating, A.C. voltages are generated in the
stator windings, and the stator supplies D. C. field current through
the diode trio, the field, TR1, and then through the grounded diodes
in the rectifier bridge back to the stator. Also, the six diodes in
the rectifier bridge change the stator A. C. voltages to a D. C.
voltage which appears between ground and the alternator 'BAT'
terminal. As alternator speed increases, current is provided for
charging the energizer and operating electrical accessories. Also,
with the alternator operating, the same voltage appears at the 'BAT'
and No. 1 terminals, and the ammeter gauge goes out to indicate the
alternator is producing a charge for the battery.
The No. 2 terminal on the alternator is always connected to the
battery. but the discharge current is limited to a negligible value
by the high resistances of R2 and R3. As the alternator speed and
voltage increase, the voltage between R2 and R3 increases to the
point where zener diode D2 conducts. Transistor TR2 then turns on
and TR1 turns off. With TR1 off, the field current and system
voltage decrease, and D2 then blocks current flow, causing TR1 to
turn back on. The field current and system voltage increase, and
this cycle then repeats many times per second to limit the
alternator voltage to a preset value.
Capacitor Cl smooths out the voltage across R3, resistor R4 prevents
excessive current through TR1 at high temperatures, and diode D3
prevents high induced voltages in the field windings when TR1 turns
off. Resistor R2 is a thermistor, which causes the regulated voltage
to vary with temperature, thus providing the optimum voltage for
charging the battery.
In order to locate and correct defects in the charging system in the
shortest possible time, the following procedures should be used.
Only a portion of these procedures need be performed. It will never
be necessary to perform all the procedures in order to locate the
To avoid damage to the electrical equipment, always observe the
Do not polarize the alternator.
Do not short across or ground any of the terminals in the charging
circuit. Never operate the alternator with the output terminal open
Make sure the alternator and battery have the same ground polarity.
When connecting a charger or a booster battery to the vehicle
battery, connect negative to negative and positive to positive.
Trouble in the charging system will show up as one or more of the
An undercharged battery as evidenced by slow cranking and low
specific gravity readings.
An overcharged battery, as evidenced by excessive water usage.
condition, as evidenced by slow cranking and low specific gravity
readings, can be caused by one or more of the following conditions
1. Insure that the undercharged condition has not been caused by
accessories having been left on for extended periods.
2. Check the drive belt for proper tens ton.
3. Inspect the wiring for defects. Check all connections for
tightness and cleanliness, including the slip connectors at the
alternator tor and firewall and the cable clamps and battery posts.
4. With ignition switch on and all wiring harness leads connected,
connect a voltmeter from:
a. Alternator "BAT" terminal to ground.
b. Alternator No. 1 terminal to ground,
c. Alternator No. 2 terminal to ground.
A zero reading indicates an open between voltmeter connection and
battery. Opens in the wiring harness connected between the No. 2
alternator terminal and battery may be be tween the terminals, at
the crimp between the harness wire and terminal, or in the wire.
5. If previous Steps 1 through 4 check satisfactorily, check
alternator as follows:
a. Disconnect battery ground cable.
b. Connect an ammeter in the circuit at the "BAT" terminal of the
c. Reconnect battery ground cable.
d. Turn on radio, windshield wipers, lights high beam and blower
motor high speed. Connect a carbon pile across the battery.
e. Operate engine at moderate speed as re quired and adjust carbon
pile as required to obtain maximum current output.
f. If ampere output is within 10 percent of rated output as stamped
on alternator frame, alternator is not defective; re check Steps 1
g. If ampere output is not within 10 percent of rated output, ground
the field winding by inserting a screwdriver into the test hole,
Fig. 4. NOTE: Tab is within 3/4" of casting surface. Do not force
screw driver deeper than 1" into end frame.
h. Operate engine at moderate speed as required and adjust carbon
pile as required to obtain maximum current output.
i. If output is within 10 percent of rated output, replace regulator
and check field winding.
j. If output is not within 10 percent of rated output, check the
field winding, diode trio, rectifier bridge and stator.
k. Remove ammeter from alternator and turn accessories off.
1. Connect a voltmeter from alternator No. 2 terminal to ground. If
reading is zero, No. 2 lead circuit is open.
2. If battery and No. 2 lead circuit check good but an obvious
overcharge condition exists, as evidenced by excessive battery water
usage, proceed as follows:
a, Separate end frames. Check field winding for shorts. If shorted,
replace rotor and regulator.
b. Connect ohmmeter using lowest range scale from brush lead clip to
end frame as shown in Step 1, Fig. 5, then reverse lead connections.
c. If both readings are zero, either the brush lead clip is grounded
or regulator is defective.
d. A grounded brush lead clip can result from omission of insulating
washer, Fig.5, omission of insulating sleeve over screw, or damaged
insulating sleeve. Remove screw to inspect sleeve. If satisfactory,
To disassemble the alternator, remove the four thru- bolts and
separate the drive end frame and rotor assembly from the stator
assembly by prying apart with a screwdriver at the stator slot. A
scribe mark will help locate the parts in the same position during
assembly. After disassembly place a piece of tape over the slip ring
end frame bearing to prevent entry of dirt and other foreign
material and also place a piece of tape over the shaft on the slip
ring end. NOTE: Use pressure- sensitive tape and not friction tape,
which would leave a gum my deposit on the shaft. If brushes are to
be reused, clean with a soft, dry cloth.
To remove the drive end frame from the rotor, place the rotor in a
vise and tighten only enough to permit removal of the shaft nut.
NOTE: Avoid excessive tightening, as this may cause distortion of
the rotor. Remove the shaft nut, washer, pulley, fan, and the
collar; and then separate the drive end frame from the rotor shaft.
Rotor Field Winding
To check for opens, connect the test lamp or ohmmeter to each slip
ring. If the lamp fails to light or if the ohmmeter reading is high
(infinite), the winding is open, Fig. 6.
The winding is checked for short circuits or excessive resistance by
connecting a battery and ammeter in series with the edges of the two
slip rings. Note the ammeter reading and refer to specifications. An
ammeter reading above the specified value indicates shorted
windings; a reading below the specified value indicates excessive
resistance. An alternate method is to check the resistance of the
field by connecting an ohmmeter to the two slip rings, Fig. 6. If
the resistance reading is below the specified value, the winding is
shorted; if above the specified value, the winding has excessive
resistance. The specified resistance value can be determined by
dividing the voltage by the current. Remember that the winding
resistance and ammeter readings will vary slightly with winding
temperature changes. If the rotor is not defective but the
alternator fails to supply rated output, the defect is in the diode
trio, rectifier bridge or stator.
Diode Trio Check
The diode trio is identified in Fig. 5. First connect an ohmmeter
using lowest range scale from brush lead clip to end frame as shown
in Step 2, Fig. 5; then reverse lead connections. If both readings
are the same, check for grounded brush lead clip caused by omission
of insulating washer, Fig. 5, omission of insulating sleeve over
screw, or damaged insulating sleeve. Remove screw to inspect sleeve.
if screw assembly is correct and both ohm-meter readings are the
same, replace regulator.
To check the diode trio, remove it from the end frame assembly by
detaching the three nuts, the attaching screw, and removing the
stator assembly. Note that the insulating washer on the screw is
assembled over the top of the diode trio connector. Connect an
ohmmeter having a 1-1/2 volt cell, and using the lowest range scale,
to the single connector and to one of the three connectors, Fig. 7.
Observe the reading. Then reverse the ohmmeter leads to the same two
connectors. If both readings are the same, replace the diode trio. A
good diode trio will give one high and one low reading. Repeat this
same test between the single connector and each of the other two
NOTE: Figs. 5 and 7 illustrate two diode trios differing in
appearance. Either one of these diode trios may be used in these
alternators, and the two are completely interchangeable.
Note that the rectifier bridge has a grounded heat sink and an
insulated heat sink connected to the output terminal. Also note the
insulating washer located between the insulated heat sink and end
frame, Fig. 8.
To check the rectifier bridge, connect the ohmmeter to the grounded
heat sink and one of the three terminals, Fig. 8. Then reverse
the lead connections to the grounded heat sink and same terminal. If
both readings are the same, replace the rectifier bridge. A good
rectifier bridge will give one high and one low reading. Repeat this
same test between the grounded heat sink and the other two terminals
and between the insulated heat sink and each of the three terminals.
This makes a total of six checks with two readings taken for each
NOTE: If rectifier bridge is constructed as shown in Fig. 9, check
with the rectifier bridge mounted in the end frame in the same
manner as Fig. 8-- except connect ohmmeter pressing down very firmly
onto flat metal connector and not onto threaded stud, Fig. 9.
The ohmmeter check of the rectifier bridge and of the diode trio is
a valid and accurate check. Do not replace either unit unless at
least one pair of readings is the same. CAUTION: Do not use high
voltage to check these units, such as a 110-volt test lamp.
Fig. 9 Rectifier Bridge Check
To replace the rectifier bridge, remove the attaching screw and the
"BAT" terminal screw and disconnect the capacitor lead. Note the
insulator between the insulated heat sink and end frame, Fig. 8.
Rectifier bridges may vary in appearance but are completely
interchangeable in these alternators.
The stator windings may be checked with a 110-volt test lamp or an
ohmmeter. If the lamp lights or if the meter reading is low when
connected from any stator lead to the frame, the windings are
grounded. If the lamp fails to light or if the meter reading is high
when successively connected between each pair of stator leads, the
windings are open, Fig. 10.
A short circuit in the stator windings is difficult to locate
without laboratory test equipment, due to the low resistance of the
windings. However, if all other electrical checks are normal and the
alternator fails to supply rated output, shorted stator windings are
indicated. Also, a shorted stator can cause the indicator lamp to be
on with the engine at low speed.
Brush Holder and
After removing the three attaching nuts, the stator and diode trio
screw, Fig. 8, the brush holder and regulator may be replaced by
removing the two remaining screws. Note the two insulators located
over the top of the brush clips in Fig. 5 and that these two screws
have special insulating sleeves over the screw body above the
threads. The third mounting screw may or may not have an
insulating sleeve, if not, this screw must not be interchanged
with either one of the other two screws, as aground may result
causing no output or uncontrolled alternator output. Regulators may
vary in appearance but are completely interchangeable in these
Fig. 10 Stator Windings Check
Slip Ring Servicing
If the slip rings are dirty, they may be cleaned and finished with
400 grain or finer polishing cloth. Spin the rotor and hold the
polishing cloth against the slip rings until they are clean. NOTE:
The rotor must be rotated in order that the slip rings will be
cleaned evenly. Cleaning the slip rings by hand without spinning the
rotor may result in flat spots on the slip rings causing brush
Slip rings which are rough or out of round should be trued in a
lathe to . 002 inch maximum indicator reading. Remove only enough
material to make the rings smooth and round. Finish with 400 grain
or finer polishing cloth and blow away all dust.
Bearing Removal and
The bearing in the drive end frame can be removed by removing the
retainer plate screws and then pressing the bearing from the end
frame. If the bearing is in satisfactory condition, it may be
reused, and it should be filled one- quarter full with Delco-
Remy lubricant No. 1948791 before reassembly. NOTE: Do not overfill,
as this may cause the bearing to overheat. Use only 1948791
To install a new bearing, press in with a tube or collar that just
fits over the outer race with the bearing and slinger assembled into
the end frame as shown in Fig. 11. It is recommended that a new
retainer plate be installed if the felt seal in the retainer plate
is hardened or excessively worn. Fill the cavity between the
retainer plate and bearing with 1948791 lubricant.
Fig. 11 Drive End Bearing (Flat Washer
May Be Used Instead of Slinger)
The bearing in the slip ring end frame should be replaced if its
grease supply is exhausted. No attempt should be made to re
lubricate and reuse the bearing. To remove the bearing from the slip
ring end frame, press out with a tube or collar that just fits
inside the end frame housing. Press from the outside of the housing
towards the inside.
To install a new bearing, place a flat plate over the bearing and
press in from the outside towards the inside of the frame until the
bearing is flush with the outside of the end frame. Support the
inside of the frame with a hollow cylinder to prevent breakage of
the end frame. Use extreme care to avoid misalignment or otherwise
placing undue stress on the
It is recommended that a new seal be installed whenever the bearing
is replaced. Press the seal in with the lip of the seal toward the
rotor when assembled--that is, away from the bearing. Lightly coat
the seal lip with oil to facilitate assembly of the shaft into the
Reassembly is the reverse of disassembly. To install the slip ring
end frame assembly to the rotor and drive end frame assembly,
remove the tape over the bearing and shaft and make sure the shaft
is perfectly clean after removing the tape. Insert a pin through the
holes to hold up the brushes. Carefully install the shaft into the
slip ring end frame assembly to avoid damage to the seal. After
tightening the thru-bolts, remove the brush retaining pin to allow
the brushes to fall down onto the slip rings. When installing the
pulley, the pulley nut must be torqued to 60 ft.lbs. If not properly
tightened, it is possible that the nut and pulley could loosen and
slip on the shaft.
To assist in tightening the pulley nut, a 5/16 inch hex hole is
provided in the end of the shaft for holding with an Allen wrench.
Also a special 15/16 inch socket wrench, Fig. 12, which is
applicable to the nut is available from the Snap-On Tool Company.
This special 1/2 inch drive socket wrench is designed with a cutout
to receive the Allen wrench and may be used in conjunction with a
torque indicating wrench. Where desired, a length of 3/8 inch pipe
may be applied to the Allen wrench to provide additional leverage
for the holding effort.
The special 15/16 inch socket wrench, Fig.12, is available from your
local Snap-On representative under their number S-8183.
Fig. 12 Torquing Pulley Nut
To check the alternator in a test stand, proceed as follows:
1. Make connections as shown in Fig. 13, except leave the carbon
pile disconnected. NOTE: Ground polarity of battery and alternator
must be the same. Use a fully charged battery and a 10 ohm resistor
rated at six watts or more between the alternator No. 1 terminal and
2. Slowly increase the alternator speed and observe the voltage.
3. If the voltage is uncontrolled with speed and increases above
15.5 volts on a 12-volt system or 31 volts on a 24-volt system,
check for a grounded brush lead clip. If not grounded, replace the
regulator and check field winding. NOTE: The battery must be fully
charged when making this check.
Fig. 13 Connections for Bench Check
4. If voltage is below 15. 5 volts on a 12-volt system, connect the
carbon pile as shown.
5. Operate the alternator at moderate speed as required and adjust
the carbon pile as required to obtain maximum current output.
6. If output is within 10 percent of rated output as stamped on
alternator frame, alternator is good.
7. If output is not within 10 percent of rated output, keep
energizer or battery loaded with carbon pile and ground alternator
field, Fig. 13.
8. Operate alternator at moderate speed and adjust carbon pile as
required to obtain maximum output.
9. If output is within 10 percent of rated output, replace regulator
and check field winding.
10. If output is not within 10 percent of rated output, check the
field winding, diode trio, rectifier bridge and stator as previously