Chevrolet 10 Series 1970 Service Manual page 400

ENGINE-ELECTRICAL 6Y-8
FIELD RELAY
" LATCH"
"F " TERMINAL
N O . 2 TERMINAL
N O . 3 TERMINAL
N O . 4 TERMINAL
slip ring end fram e and a re jointed to the stator windings
at three intern ally located term in als.
Diodes are mounted in heat sinks to p rovide adequate
heat dissipation. The six diodes replace the separately
mounted r e c tifie r as used in other types o f application.
The diodes change the D elcotron A .C . current to D.C.
current.
Th ree regu lators a re availa b le on truck m odels. A
double contact two unit type, a tran sistor unit with an
internal fie ld rela y and a com pletely static full tran sistor
regu lator (130 amp gen erator only). The function o f these
regu la tors in the charging system is to lim it the gen era ­
to r voltage to a p r e -s e t value by controlling the gen erator
fie ld current.
The two unit double contact unit and the junior tran­
s is to r regu lator (when applicable) use the fie ld re la y to
turn out the indicator lam p. The rela y unit allow s the
lamp to light (as a bulb check) with the ignition key on
and engine not running. When the engine is started and
the gen erator begins to charge, the indicator light goes
out indicating that the system
The double-contact regu lator assem bly (fig . 2c) con­
sists o f a double-contact voltage regu lator unit and a
fie ld rela y unit. Th is unit uses two sets of contact points
on the voltage regu lator unit to obtain d esired field
excitation under v a ria b le
when used with the special 63 amp a ir conditioning model
gen erator (4 ohm fie ld c o il), uses a fie ld discharge diode
in tern ally in the fie ld circu it (fig. 2c). The added diode
adapts the regu lator to handle the higher fie ld current and
enables it to absorb the in creased inductive volta ges o f
the fie ld coil with sa tisfa ctory contact point lift. A w ir ­
ing diagram o f the regu lator internal circu it is illu strated
in F igu re 2c.
The light duty tra n s is to r
assem b ly composed p rin cip a lly o f tra n sistors, diodes,
re s is to rs , a capacitor, and a th erm istor to form a com ­
p letely static voltage regulating unit in combination with
a conventional vibrating type fie ld relay.
The tra n sisto r is an e le c tr ic a l device which lim its the
gen erator voltage to a p re s e t value by con trollin g the
VOLTAGE
REGULATOR
F ig . 2 c —D oub le C o n ta c t R egulator
is operating n orm ally.
conditions. T h is regulator,
regulator (fig . 3c) is an
gen erator field current. The diodes, capacitor and r e ­
s is to rs act together to aid the tra n sisto rs in controlling
the gen erator voltage. T h is is the only function that the
regu lator p erfo rm s in the charging circu it. The th erm ­
is to r p rovid es a tem perature-com pensated voltage set­
ting. A w irin g diagram of this reg u la to r' s internal circu it
is shown in Figu re 3c.
The voltage at which the gen erator operates is d eter­
mined by the regu lator adjustment. The regu lator voltage
setting can be adjusted extern ally by rem ovin g a pipe
plug in the co ver (fig . 3c) and turning the adjusting arm
inside the regu lator. T h is procedure is explained in the
follow in g section, and p erm its
without rem oving the co ver.
The full tra n sistor regu lator used with the 130 amp
gen era to r (fig . 4c) is a com pletely static unit composed
p rin cip a lly o f tra n sisto rs, diodes, cap acitors and r e ­
s isto rs. The ro to r fie ld current is controlled by d iffe r ­
ences in internal voltage and resistance values acting on
the tra n sisto rs, diodes and re s is to rs within the regu lator.
T h is unit has certain
assem blies,,
1. The regu lator units a re not grounded in the regu la ­
tor. They a re connected to a third lead which is
brought out of the regu lator to a ground location.
2. It does not use a th erm istor fo r automatic tem p era ­
ture compensation, because the quantity o f current
handled by the system does not w arrant the minute
co rrectio n s this unit is designed to make.
3. The regu lator its e lf is not grounded.
4. It is used with an am m eter and a fie ld rela y in the
system .
W irin g harnesses a re protected by fusible links. A
fusible link is a length o f special w ire , norm ally four
gauges sm a ller than the circu it it is protecting, used
in circu its that are not
ignition circu it. The same siz e
insulation must be used when replacing a fusible link.
The links a re located in the engine com partm ent w irin g
harnesses and each link w ill be identified with its gauge
size . On m ost m odels there is a 16 gauge, red w ire
regu lator adjustments
d ifferen ces f r o m the other
norm ally fused such as the
w ire with a hypalon
CHEVROLET TRUCK SERVICE MANUAL