Chevrolet DB90 Series, Руководство по обслуживанию

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S ec. 12-209
SECTION 12
CltaMii
Z le e b U c a l
and Onit^uune^tti
Inform ation pertaining to CHASSIS ELECTRICAL AND INSTRUMENTS (SEC.
12) as d escrib ed in the 1970 Heavy Duty Truck S erv ice Manual ST 135-70 and Sup­
plem ent ST332-71 is applicable to v e h ic le s covered by th is supplem ent with the
exception of the following:
WIRING DIAGRAM S
W iring d iagram s, included in "Wiring D ia­
gram s" in sectio n 12 of S erv ice Manual ST 135-70,
show e le c tr ic a l c ir c u its and connections for stan­
dard and optional equipment u sed on each truck
s e r ie s covered by th is supplem ent. The truck
s e r ie s to which each diagram applies is also
shown on each diagram .
NOTE: On s e r ie s 90 v e h ic le s, a sch em atic
diagram of the e le c tr ic a l sy ste m is located on
inner sid e of con sole panel a c c e s s cover.
W IRING HARNESSES AND WIRES
On v e h ic le s equipped with the V 6-401M or
V 6-478 gasoline engine, except S e r ie s RM80,
a 1.52 ohm r e sista n c e w ire is used in the engine
w iring h a rn ess, connecting the "IGN" term inal of
the ignition sw itch to the p o sitiv e (+) term in al on
the ignition c o il. The proper length w ire is u sed to
provide the c o r rect r e sista n c e . T his w ire is iden­
tified on applicable w iring diagram s in "Wiring
D iagram s in Section 12 of S erv ice Manual Supple­
m ent ST332-71 a s "20-BLK." or "20-WHT. ORN.
& P P L . CR. TR." DO NOT u se regular copper
w ire in place of th is r e sista n c e w ire.
On v e h ic le s equipped with the V 8-637 gasolin e
engine, a 1.35 ohm r e sista n c e w ire is used in the
engine w iring h arn ess to connect the "IGN” te r m ­
inal of the ignition sw itch to the p o sitiv e (+) te r m ­
inal on the ignition c o il. The proper length w ire is
u sed to provide the c o r r e ct r e sista n c e . T his w ire
is identified on applicable w iring diagram s in
"Wiring D iagram s" booklet X -7205 a s "20-BLK."
DO NOT u se regular copper w ire in p lace of this
r e sista n c e w ire.
On S e r ie s RM80, a 1.52 ohm ignition coil
r e s is t o r is connected into the circu it betw een "IGN”
term in a l on ignition sw itch and p o sitiv e (+) term ­
inal on the ignition c o il. The r e s is to r p rovid es in­
c r e a se d voltage during engine cranking.
MAINTENANCE AND REPAIR
TESTING CIRCUITS
A carefu l study of the w iring diagram s should
b e made to determ ine the sou rce and flow of cu r­
rent through each e le c tr ic a l circ u it. When a circu it
is thoroughly understood, a poin t-to-p oin t check can
be made with the aid of the applicable w iring dia­
gram to determ ine location of trouble. Any circu it
can be te sted for continuity o r short cir c u its with
a 2-candlepow er te st light or low -read in g v o lt­
m eter.
Each w ire in the e le c tr ic a l sy ste m is of a
sp e c ific s iz e a s designated on the W iring D ia­
g ra m s. When replacing w ir e s, the co r r e ct s iz e as
indicated m ust be used . N ever rep lace a w ire with
one of a s m a lle r s iz e .
CHEVROLET SERIES 70-90 HEAVY DUTY TRUCK SHOP MANUAL SUPPLEMENT