
ENGINE-ELECTRICAL 6Y-8
1
FIELD RELAY^I^p2
"LATCH"
^PFN?^
"P1
TERMINAL
JyJvJCTl^
NO. 2 TERMINAD^5^^^«
NO.
3 TERMINAL ^S5«£
NO.
4 TERMINAL ^^^
m
# / VOLTAGE
¥ REGULATOR
1
ACCESS PLUG TO
VOLTAGE ADJUSTMENT
No 4 TERMINAL
Double Contact
Fig.
2c—Voltage Regulator Assemblies
Transistor
regulator to handle the higher field current and enables it
to absorb the increased inductive voltages of the field
coil with satisfactory contact point life.
The double-contact regulator assembly (fig. 2c) con-
sists of a double contact voltage regulator unit and a field
relay unit. This unit uses two sets of contact points on
the voltage regulator unit to obtain desired field excita-
tion under variable conditions. Internal circuit wiring
diagrams of the double contact regulator are shown in
Figures 3c and 4c.
The transistor regulator (fig. 2c) is an assembly com-
posed principally of transistors, diodes, resistors, a
capacitor, and a thermistor to form a completely static
voltage regulating unit in combination with a conventional
vibrating type field relay.
The transistor is an electrical device which limits the
generator voltage to a preset value by controlling the
generator field current. The diodes, capacitor and re-
sistors act together to aid the transistors in controlling
the generator voltage. This is the only function that the
regulator performs in the charging circuit. The
thermistor provides a temperature-compensated voltage
setting. Wiring diagrams of the transistor regulator are
shown in Figures 3c and 4c.
The voltage at which the generator operates is deter-
mined by the regulator adjustment. The regulator voltage
setting can be adjusted externally by removing a pipe plug
in the cover (fig. 2c) and turning the adjusting arm inside
the regulator. This procedure is explained in the followr
ing section, and permits regulator adjustments without
removing the cover.
FUSIBLE
DOUBLE CONTACT
FUSIBLE LINK-^
JUNCTION HORN
BLOCK RELAY
RESISTOR
Q FIELD Q>
DELCOTRON TR-
TRANSISTOR
FUSIBLE LINK-
Fig.
3c-Circuity - Voltage Regulator Assemblies (Except Corvette)
CHEVROLET CHASSIS SERVICE MANUAL

ENGINE-ELECTRICAL 6Y-9
63 AMP 1
MODELS ONLY'
BATTERY FUSIBLE
LINK
HORN
FUSIBLE LINK'
TRANSISTOR
FUSIBLE LINK'
Fig.
4c— Circuitry - Voltage Regulator Assemblies (Corvette)
Engine compartment wiring harness incorporates sev-
eral fusible links. Each link is identified with its gage
size. A fusible link is a length of special wire (normally
four wire gages smaller than the circuit it is protecting)
used in wiring circuits that are not normally fused, such
as the ignition circuit. The same size wire with a hypalon
insulation must be used when replacing a fusible link.
The links are:
1.
The pigtail lead at the battery positive cable (except
Corvette) is a 14 gage, brown fusible link protecting
the 10 gage battery charging circuit. This wire is an
integral part of the battery cable assembly and serv-
icing requires replacing the complete battery cable
assembly. On Corvette models this link is installed
as a molded splice at the solenoid "Bat" terminal
and servicing requires splicing in a new link.
2.
A 16 gage black fusible link is located at the horn
4.
relay to protect all unfused wiring of 12 gage or
larger. It is installed as a molded splice and serv-
icing requires splicing in a new link.
The generator warning light and field circuitry (16
gage wire) is protected by a fusible link (20 gage
orange wire) used in the "battery feed to voltage
regulator #3 terminal" wire. The link is installed as
a molded splice in the generator and forward lamp
harness and is serviced by splicing in a new 20 gage
wire as required.
The ammeter circuit on all models is protected by
two orange, 20 gage wire fusible links installed as
molded splices in the circuit at the junction block or
the solenoid "Bat" terminal (Corvette only) and at
the horn relay. Each link is serviced by splicing in a
new 20 gage wire as required.
MAINTENANCE AND ADJUSTMENTS
At regular intervals, inspect the terminals for cor-
rosion an4 loose connections, and the wiring for frayed
insulation. Check mounting bolts for tightness. Check the
drive belt for alignment, proper tension and wear. Be-
cause of the higher inertia and load capacity of the rotor
used in A.C. generators, PROPER BELT TENSION is
more critical than on D.C. generators.
Since the Delcotron and its companion regulator are
designed for use on negative polarity systems only, the
following precautions must be observed. Failure to ob-
serve these precautions may result in serious damage to
the charging system.
1.
When installing a battery, always make absolutely
sure the ground polarity of the battery, generator and
regulator is the same.
2.
When connecting a booster battery, make certain to
connect the correct battery terminals together.
3.
When connecting a charger to the battery, connect the
correct charger leads to the battery
%
terminals.
4.
Never operate the generator on an uncontrolled open
TO SOLENOID
BAT ACC RES. WIRE
Fig.
5c—Typical Wiring Diagram Showing Lead Connections
CHEVROLET CHASSIS SERVICE MANUAL

ENGINE-ELECTRICAL 6Y-J2
Fig.
8c—Ammeter Method Test Connections
10.
Turn off ignition, disconnect battery ground cable,
and remove all test equipment.
11.
li the Delcotron meets the test specifications, the
problem is not in the generator.
12.
Ti the Delcotron fails to meet the test specifications,
remove it and perform bench tests and make repair
needed.
DELCOTRON DIODE AND FIELD TEST (Fig. 9c)
NOTE:
These tests will indicate good,, shorted
or open field or shorted diode but will not indi-
cate a failed open diode. If output was low and
following tests show good, refer to service op-
erations to determine cause and repair.
1.
Disconnect battery ground cable at battery.
2.
Positive diodes (Test A) connect an ohmmeter be-
tween "R" terminal and "BAT" terminal and note
Fig.
9c-Deicotron Diode and Field Test
reading, then reverse the leads at same terminals
and note this reading. Meter should read high re-
sistance in one direction and low in the other.
3.
Negative diodes (Test B) connect ohmmeter between
"R" terminal and "GRD" and note reading, then
reverse the leads and note this reading. Meter
should read high in one direction and low in the
other.
NOTE:
A high or low reading in both directions
indicates a defective diode.
4.
Open Field Check:
a. Connect an ohmmeter from "F" terminal to
"GRD"
terminal stud and note reading on the
lowest range scale. Meter should read 7 to
20 ohms.
b.
If meter reads zero or excessively high resist-
ance, the Delcotron is faulty.
5. If above tests indicate a defective Delcotron, remove
and completely check Delcotron as outlined under
''Service Operations".
INDICATOR LAMP/INITIAL FIELD
EXCITATION CIRCUIT TESTS (Fig. 10c)
On standard models the indicator lamp circuit provides
initial field excitation (causing lamp to glow). The light
is cancelled by closing the field relay which applies bat-
tery voltage to both sides of bulb (bulb goes out).
The indicator light should glow when ignition switch is
"ON"
and go out almost immediately when engine starts.
Ammeter equipped vehicles use the same initial field
excitation and control circuits as the indicator lamp ex-
cept the lamp is omitted. The continuity tests on both
type vehicles can be made as follows:
If Lamp Fails to Glow or Ammeter Fails to
Function the Possible Causes are:
1.
Faulty bulb or bulb socket.
2.
Faulty ammeter.
3.
An open circuit in wiring, regulator, or field.
4.
A shorted positive diode—(may also cause glow with
ignition switch "OFF").
TEST AS FOLLOWS:
1.
Disconnect connector from regulator and turn
ignition switch to "ON". Connect a test lamp from
connector terminal "4" to ground (fig. 10c, Step 1)
and note test lamp.
a. Lamp fails to glow—check for faulty bulb, socket
or open circuit between switch and regulator con-
nector. Repair as needed.
b.
Light goes on—failure is in regulator, Delcotron,
or wire between "F" terminals on regulator and
Delcotron. Go to Step 2.
2.
Disconnect lamp lead at ground end and connect be-
tween connector "F" and "4" terminals (fig. 10c,
Step 2), and note lamp:
a. Test Lamp glows—problem is in regulator. An
open circuit in regulator or relay is stuck dosed.
See "Service Operations" for repair.
b.
Fails to glow—problem is in wire between "F"
terminals on generator and regulator or infield
windings. Go to Step 3.
3.
Disconnect test lamp at connector "F" terminal and
CHEVROLET CHASSIS SERVICE MANUAL

ENGINE-ELECTRICAL 6Y-13
F 2 3 4
f 2 3 4
F 2 3 4
Fig.
10c—Initial Field Excitation Circuit Tests
connect to "F" terminal on Delcotron (fig. 10c,
Step 3), and note lamp:
a. Lamp glows-an open circuit in wire between "F"
terminals—correct as needed.
b.
Fails to glow—Delcotron field has open circuit,
see "Service Operations" to repair %
If Lamp Fails to Go Out, or if Ammeter Shows
Discharge the Possible Causes are:
1.
Loose drive belt—adjust as necessary.
2.
Faulty field relay—(see relay test and adjustment).
3.
Defective Delcotron—(see Delcotron output test).
4.
At normal idle—parallel resistance wire open (see
Resistance test). On ammeter models the initial
field excitation wire to "ACC" terminal is open.
5. Switch off—positive diode shorted (see Diode test).
FIELD CIRCUIT RESISTANCE
WIRE CHECKS
The resistance wire is an integral part of the ignition
harness. However, the resistance wire is not solderable;
it must be spliced with a crimp-type connector. It is
rated at 10 ohms, 6.25 watts minimum.
The check for an open resistor or field excitation wire
(connected to the ignition switch "ACC" terminal) is as
follows:
1.
Connect a test lamp from the wiring harness con-
nector terminal "4" to ground as shown in Figure
10c (Step 1).
2.
Turn the ignition switch to the "ON" position and
note test bulb.
a. Test lamp glows—resistance is O.K.
b.
Test lamp does not glow—the resistor is open
circuited—note also that dash lamp does not glow
during this test because series resistance of the
2 bulbs causes amperage to be too low.
VOLTMETER
3 4
WIRING*
HARNESS
CONNECTOR
Fig.
11c—Testing Field Relay
CHEVROLET CHASSIS SERVICE MANUAL

ENGINE-ELECTRICAL 6Y-14
VOLTMETER
WIRING HARNESS
CONNECTOR
Fig.
12c—Field Relay Closing Voltage Test
FIELD RELAY CHECKS AND ADJUSTMENT
To check for a faulty relay proceed as follows:
1.
Connect a voltmeter into the system at the regulator
No.
2 terminal to ground (fig. lie).
2.
Operate the engine at fast idle (1500 to 2000 rpm) and
observe voltmeter reading.
3.
If voltmeter shows zero voltage at regulator, check
circuit between No. 2 terminal on regulator to "R"
terminal on Delcotron.
4.
If voltage at regulator exceeds closing voltage
Fig.
13c—Adjusting Field Relay Closing Voltage
specification and light remains on, regulator field
relay is faulty (Refer to specifications). Check and
adjust regulator as follows:
CLOSING VOLTAGE ADJUSTMENT
•1.
Make connections as shown in Figure 12c using a 50
ohm variable resistor.
NOTE: This gives us a variable resistance in
series from a hot lead to the relay coil.
2.
Turn resistor to "open" position.
3.
Turn ignition switch off.
4.
Slowly decrease resistance and note closing voltage
of the relay. Adjust by bending heel iron in the man-
ner illustrated in Figure 13c.
OTHER HARNESS CHECKS
Other wires in the charging system harness need be
checked for continuity by use of an ohmmeter or a test
ligjit (12 Volt). Connect the test so the wire in question is
in series in the test circuit.
SERVICE OPERATIONS
Service Procedures described in this section are for
the 5.5" aluminum and 6.2" perforated stator Delcotrons
(fig. 14c). Where important differences are encountered
separate mention will be made of the two generators.
GENERATOR
REMOVAL AND INSTALLATION
1.
Disconnect the battery ground strap at battery to
prevent damaging diodes.
2.
Disconnect wiring leads at Delcotron.
3.
Remove generator brace bolt, (if power steering
equipped, loosen pump brace and mount nuts) then
detach drive belt (belts).
4.
Support the generator and remove generator mount
bolt (6.2" Delcotron uses 2 mount bolts) and remove
from vehicle.
5.
Reverse the removal procedure to install then adjust
drive belt.
PULLEY REPLACEMENT
5.5" Delcotron
Single Groove Pulley
1.
Place 15/16" box wrench on retaining nut and insert
a 5/16" alien wrench into shaft to hold shaft while
removing nut (fig. 15c).
2.
Remove washer and slide pulley from shaft.
3.
Reverse Steps 1 and
2
to install, use a torque wrench
with a crow-foot adapter (instead of box wrench) and
torque the nut to 50 ft. lbs. (fig. 16c).
Double Groove Pulley
1.
Place a 15/16" socket (with wrench flats on the drive
CHEVROLET CHASSIS SERVICE MANUAL

ENGINE-ELECTRICAL
6Y-16
POINT
OPENINGJL
Fig. 17c-6.2"
Brush
Holder
Assembly
5. Rearrange leads as shown in Figure 18c with right-
hand brush lead connected under the right hand hex-
head stud.
6. Remove pin and attach terminal cover with two
screws, making sure leads are not caught under-
neath the cover.
DOUBLE CONTACT REGULATOR
While most regular adjustments are made on the vehi-
cle as outlined under "Maintenance and Adjustments",
the regulator may be removed for field relay point and
air gap adjustment. However, voltage regulating contacts
should never be cleaned as they are made of special
material that may be destroyed by cleaning with any
abrasive material.
NOTE:
A sooty or discolored condition of the
contacts is normal after a relatively short
period of operation.
Fig. 19c—Checking Field Relay Point Opening
REMOVAL AND INSTALLATION
To remove the regulator assembly, disconnect the bat-
tery ground cable and the wiring harness connector at the
regulator, then remove the screws securing the regulator
to the vehicle.
Electrical settings must be checked and adjusted after
making mechanical adjustments. Before installing regu-
lator cover, make sure the rubber gasket is in place on
the regulator base.
MECHANICAL ADJUSTMENTS
NOTE:
Only an approximate voltage regulator
air gap setting should be made by the "feeler
gauge" method.
BRUSH
LEAD
BRUSH
LEAD
RELAY
^B-/lliLlK
CONDENSER
LEAD
GROUND
LEAD
STUD
AIR GAP
(Check
With
Points
Just
Touching)
Fig.
18c—Lead
Arrangement
after
Assembly
Fig. 20c—Checking Field Relay Air Gap
CHEVROLET CHASSIS SERVICE MANUAL

MAINTENANCE AND ADJUSTMENTS
ENGINE-ELECTRICAL 6Y-19
PERIODIC MAINTENANCE
BREAKER POINT SYSTEM
The distributor breaker points and spark plugs are the
only ignition system components that require periodic
service. The remainder of the ignition system requires
only periodic inspection to check operation of the units,
tightness of the electrical connections, and condition of
the wiring. When checking the coil, test with a reputable
tester.
Breaker type distributors are equipped with cam lubri-
cator and should have the wick replaced at the same time
contact point set is replaced. It is not necessary to
lubricate the breaker cam when using a cam lubricator.
Do not attempt to lubricate the wick - Replace when
necessary. When installing a new wick, adjust its posi-
tion so the end of the wick just touches the lobe of the
breaker cam.
Distributor shaft lubrication is accomplished by a
reservoir of lube around the mainshaft in the distributor
body.
BREAKERLESS SYSTEM
Since there are no moving parts in the ignition pulse
amplifier unit mounted forward of the radiator bulkhead,
and the distributor shaft and bushings have permanent
type lubrication, no periodic maintenance is therefore
required for the breakerless ignition system. The dis-
tributor lower bushing is lubricated by engine oil through
a splash hole in the distributor housing, and a housing
cavity next to the upper bushing contains a supply of
lubricant which will last between overhaul periods. At
time of overhaul, the upper bushing may be lubricated
by removing the plastic seal and then adding SAE 20 oil
to the packing in the cavity. A new plastic seal will be
required since the old one will be damaged during
removal.
Tachometer readings for test purposes can be made on
the primary circuit of the breakerless ignition system in
the same manner as on the conventional ignition system,
however before attempting to connect a test tachometer
into the primary circuit check with your instrument
supplier to insure that satisfactory readings can be
obtained and the breakerless system will not be damaged
by the tachometer that is to be used,
IGNITION COIL CHECK (BREAKERLESS)
The ignition coil primary can be checked for an open
PULSE
AMPLIFIER
IGN. SWITCH WIRE
"("IGN" TERMINAL)
-E3 IJU
12
WHITE-
-20 BLACKf' • 12 WHITE-
Fig.
3i—
Breakerless Ignition System
condition by connecting an ohmmeter across the two
primary terminals with the battery disconnected. Pri-
mary resistance at 75
°F.
should be between .35 and .55
ohm. An infinite reading indicates the primary is open.
For the engine to run but miss at times, the primary
open may be of the intermittent type.
The coil secondary can be checked for an open by con-
necting an ohmmeter from the high tension center tower
to either primary terminal. To obtain a reliable reading,
a scale on the ohmmeter having the 20,000 ohm value
within, or nearly within, the middle third of the scale
should be used. Secondary resistance at 75°F. should be
between
8,000
and 12,500 ohms. If the reading is infinite,
the coil secondary winding is open.
A number of different types of coil testers are avail-
able from various test equipment manufacturers. When
using these testers, follow the procedure recommended
by the tester manufacturer.
tester will properly
NOTE:
Make sure the
check this special coil.
SPARK PLUGS
Should be removed, inspected cleaned and regapped at
tune-up. Defective plugs should be replaced, see Servic-
ing of Units Off the Vehicle.
SERVICE OPERATIONS
DISTRIBUTOR CONTACT POINTS
CLEANING
Dirty contact points should be dressed with a few
strokes of a clean, fine-cut contact file. The file should
not be used for other metals and should not be allowed to
become greasy or dirty. Never use emery cloth to clean
contact points. Contact surfaces, after considerable use,
may not appear bright and smooth, but this is not neces-
sarily an indication that they are not functioning satis-
factorily. Do not attempt to remove all roughness nor
dress the point surfaces down smooth; merely remove
scale or dirt.
Badly burned or pitted contact points should be re-
placed and the cause of trouble determined so it can be
eliminated. High resistance or loose connections in the
condenser circuit, oil or foreign materials on the contact
surfaces, improper point adjustment or high voltages may
CHEVROLET CHASSIS SERVICE MANUAL

ENGINE-ELECTRICAL 6Y-29
each capacitor (not illustrated). The capacitor is
shorted if both readings are zero.
6. Resistor Rl: The resistor is open if both readings
are infinite.
7. Resistor R2: Use an ohmmeter scale on which the
1800 ohm value is within, or nearly within, the
middle third of the scale. If both readings are infi-
nite, the resistor is open.
8. Resistor R3: Use an ohmmeter scale on which the
680 Ohm value is within, or nearly within, the middle
third of the scale. If both readings are infinite, the
resistor is open.
9. Resistor R4: Select an ohmmeter scale on which the
15000 ohm value is within, or nearly .within, the
middle third of the scale. If either reading is infi-
nite, the resistor is open. ~
10.
Resistor R5: Use the lowest range ohmmeter scale.
The resistor is open if either reading is infinite.
NOTE:
This resistor on some applications may
be located in the vehicle wiring harness, and not
on the panel board.
11.
Resistor R6: An ohmmeter scale on which the 150
ohm value is within or nearly within, the middle
third of the scale should be used. If both readings
are infinite, the resistor is open.
REASSEMBLY
During assembly, coat with silicone grease both sides
of the flat insulators used between the transistors and
heat sink, and also the heat sink on the side on which the
transistors are mounted. The silicone grease, which is
available commercially, conducts heat and thereby pro-
vides better cooling.'
IGNITION PULSE AMPLIFIER
R-5
C-3 Ju
MAGNETIC PULSE
DISTRIBUTOR
IGNITION SWITCH REPLACEMENT (Figs.
21
i to 23i)
CHEVROLET, CHEVY II AND CORVETTE
1.
Raise hood and disconnect battery ground cable from
battery.
2.
Remove lock cylinder by positioning switch in "off"
position and inserting wire in small hole in cylinder
face. Push in on wire to depress plunger and con-
tinue to turn key counter-clockwise until lock cylin-
der can be removed.
3.
Remove the metal ignition switch nut from the pas-
senger side of the dash using Tool J-7607 (Fig. 21i).
4.
Pull the ignition switch out from under the dash and
remove the wiring connectors.
5. To remove the "theft resistant" connector, the
switch must be out from under the dash as outlined
in Step 4. Using a screw driver unsnap the locking
tangs on the connector from their position on the
switch as shown in Figure 22i. Unplug the connector.
6. Snap the connector into place on a new ignition
switch.
7. Place the switch into position from behind the dash
and install the metal ignition switch nut.
8. Install the lock cylinder.
9. Install the battery cable to the battery and lower the
hood.
CHEVELLE
1.
Disconnect battery ground cable.
2.
Remove ash tray, retainer attaching screws and
retainer.
3.
Remove A/C distributor duct retaining screws and
duct.
Fig.
19i—Pulse Amplifier Internal Circuitry
Fig.
20i—Transistor Checking
CHEVROLET Oi