Chevrolet 70 Series 1970, Service Manual

Page: 759 / 841

CHASSIS ELECTRICAL AND INSTRUMENTS 12-13
break er. R elay operating c o il term in al No. 3 is fed
from the "ACC" p o sitio n of the control sw itch when
sw itch is in "IGN" or "ACC" p o sitio n . When relay
operating c o il is en ergized , contacts c lo se to com ­
p lete circu it from battery to a c c e s s o r y bus bar
and circu it b reak ers
8
, 9, 10 and 11 shown in fig ­
ure 7.
GENERATOR TELL-TA LE RELAY
(WHEN USED)
The generator t e ll- t a le relay is u sed on som e
v e h ic le s to control the c ircu it to the generator no­
charge te ll-ta le lamp.
R elay term inal No. 1 is fed through a 15-am p
fu se on the ignition bus bar when engine control
sw itch is in "IGN" p o sitio n . When control sw itch is
placed in "IGN" p o sitio n , current from the battery
w ill flow through the generator t e ll-t a le lam p and
relay term in al N o. 1 to ground through term in al
No. 2. When engine i s started , current from gen­
erator "R" term in al w ill flow through relay op er­
ating co il windings (term in al No. 3) causing contact
points to open, thus breaking the circu it to the t e ll­
ta le lam p.
R elay is non-adjustable or repairable, th e r e ­
fo r e if it b eco m es inoperative, rep lace.
HORN RELAY
R efer to applicable w iring diagram fo r w iring
connections at horn relay.
Horn button in cen ter of steerin g w heel is con­
nected in s e r ie s with the rela y operating c o il at r e ­
lay term in al No. 2. When circu it through relay
operating c o il is com pleted at the horn button, a
s m a ll amount of current flow s from the battery
through the co il winding. With winding en ergized ,
arm ature is attracted to c o re and points c lo s e .
Current from the battery (No. 1 term inal) then
flo w s d irectly through relay contacts and out No.
3 term in al to the horn. The relay thus p rovid es a
higher voltage to the horn by avoiding voltage drop
through the long circu it through the horn button.
The relay is non-adjustable or repairable, th e r e ­
fo re if it b ecom es in op erative, rep la ce.
TRAILER I.C.C. MARKER LAMP
RELAY (WHEN USED)
The tr a ile r I.C .C . m arker lamp relay i s mount­
ed on the junction b lock at right rear of cab on
conventional cab m od els and on the steerin g column
support on s e r ie s 70 through 80 tilt cab m o d els.
R efer to applicable w iring diagram in "Wiring D ia­
gram s" booklet for w irin g connections at rela y .
The m arker lamp sw itch on instrum ent panel
is connected in s e r ie s with main ligh t sw itch and
operating c o il of I.C .C . m arker lam p relay o p er­
ating co il at term inal No. 3.
When the main light sw itch and the m arker
lamp sw itch a r e p laced in "ON" p osition , a sm a ll
amount of current w ill flow through the relay co il
winding. With winding en ergized , arm ature i s a t­
tracted to co re and p oin ts c lo s e . Current from the
battery (No. 1 term inal) then flow s d irectly through
relay contacts and out term inal No. 2 to com plete
circu it to rea r I.C .C . m arker lam ps.
If opening voltage is not within lim its lis te d in
"Specifications" at end of th is se ctio n , rep lace the
relay.
HEATER AND RADIO PANEL
(ALUM. TILT CAB)
IMPORTANT: B efo re rem oving the h eater and
radio panel located in the co n so le to right of driver,
disconnect negative cable(s) from the battery to
prevent accidental shorting.
1. R em ove sc r e w s w hich attach a c c e s s panel
to r ea r of co n so le, then rem ove a c c e s s panel.
2. R em ove s ix sc r e w s which attach heater and
radio panel to con sole, then lift panel up out of
co n so le enough to rem ove attaching w ir e s and lin k ­
age from under panel and through a c c e s s panel
opening. R em ove knobs a s n e c e ssa r y to rem ove
sw itch es and con trols from a c c e s s panel.
3. P o sitio n sw itch es and controls on panel and
connect w iring to sw itch es.
4. P o sitio n panel in co n so le and in sta ll sc r e w s
to attach.
5. In stall a c c e s s panel to rea r of co n so le, then
connect negative battery cable(s) to battery and
check operation of each unit.
STARTER SWITCH
On conventional cab m od els and S e r ie s 70-80
t ilt cab m odels the ignition o r control sw itch is
mounted on the dash panel. The sta rtin g circu it
i s en ergized by placing the sw itch in “ START”
p o sitio n . For inform ation rela tiv e to rep lacin g this
sw itch, refer to "Ignition Switch Replacem ent"
under "IGNITION SYSTEM" in ENGINE ELEC­
TRICAL (SEC.
6
Y) of th is manual.
The alum tilt cab m odels are equipped with
two m om entary-on push button-type sta r te r
sw itc h e s. The sw itch mounted on the con sole below
the gauge panel can be en ergized only when the
engine control sw itch is in the "IGN" position . The
au xiliary sta rt sw itch is located in sid e the left
fram e ra il and is p rotected by a rubber boot. This
sw itch is fed through the No.
8
circu it breaker
when the engine control sw itch is in the "ACC” or
"IGN" p osition .
CHEVROLET SERIES 70-90 HEAVY DUTY TRUCK SHOP MANUAL