Chevrolet 10 Series 1970, Service Manual

Page: 402 / 671

ENGINE-ELECTRICAL 6Y-10
6, Do not attempt to p o la riz e the gen erator.
7. Do not disconnect lead at gen erator without fir s t
disconnecting battery ground cable.
Trou ble in the A .C . charging system w ill usually be
indicated by one o r m ore o f the follow in g conditions:
1. Faulty indicator lam p o r am m eter operation.
2. An undercharged b attery (usually evidenced by slow
cranking speeds).
3. An overch arged b attery (usually evidenced by e x ­
c e s sive battery w ater usage).
4. E xcessive gen era tor noise or vibration.
D escrib ed below a re a s e r ie s o f o n -th e-veh icle quick
checks which a re designed to assist the s e rv ic e techni­
cian in locating troubles within the variou s components
o f the engine e le c tr ic a l system . Additional checks, ad­
justm ents and overhaul proced u res of these components
a re also d escrib ed in the "C h a rg in g S y stem s-S ervice
O perations
S ec tio n " and should be r e fe r r e d to as
n ecessary.
STATIC CHECKS
B e fo re making any e le c tr ic a l checks, p e rfo rm the
follow in g static checks:
1. Check fo r loose fan belt.
2. Check fo r d e fective b attery. (R e fe r to B attery.)
3. Inspect a ll connections, including the slip -on con­
nectors at the regu la tor and D elcotron.
NOTE: Do not short fie ld to ground to check if
gen erator is charging since this w ill serio u sly
damage the charging system .
SYSTEM C O N D IT IO N TEST
( 5 .5 " - 6 .2 " DELCOTRON SYSTEMS)
T h is test is used to indicate the o v e ra ll condition o f
the charging system (both good and d e fe c tiv e ) and to
isola te the malfunctioning unit if the system is d efective.
1. With ignition o ff, p e rfo rm the p re s c rib e d Static
Checks outlined in this section. Then set hand brake
and shift tran sm ission into neutral.
F ig . 5 c —A d ju s t
2. Connect a v o ltm eter from junction block on horn
re la y to ground at regu lator base.
C A U TIO N : Be_ sure m eter clip does not touch a
re s is to r o r term in al extension under regu lator.
3. Connect a tachom eter on engine.
4. M odels equipped with Indicator Lamp: Turn ignition
switch on " O N " position and check indicator lamp.
If lamp fa ils to glow, p e rfo rm appropriate tests and
c o rrectio n s (Indicator Lam p C ircu it T e s ts ) b efore
continuing.
M odels equipped with A m m eter: Turn ignition
switch to " A C C " with an a c c e s s o ry on and check
a m m eter. If am m eter fa ils to read d isch arge, check
a m m eter circu it b efo re continuing.
5. M odels equipped with Indicator Lamp: If lamp glow s,
start the engine and run it at 1500 rpm o r above.
Check indicator lamp. If lamp fa ils to go out, p e r ­
form appropriate test and correctio n s (Indicator
Lamp C ircu it T e s t) b efo re continuing.
M odels equipped with A m m eter: If am m eter reads
disch arge, start the engine and observe am m eter. If
m eter fa ils to m ove toward charge (from o rigin a l
position), p e rfo rm appropriate test and correctio n s
(F ie ld C ircu it T e s ts ) b efo re continuing.
NOTE: A t this point a fie ld circu it has been
established and any other problem w ill lie in
gen erator o r regu lator.
6. Turn on high-beam headlights and heater blow er
m otor to high speed, run engine at or above 1500
rpm (fo r a few minutes, i f n ecessa ry) and read the
voltage on m eter.
NOTE: V oltage w ill not g rea tly exceed 12 1/2
volts until the battery develops a surface charge,
a few minutes gen era lly , unless the battery is
s e v e re ly discharged or is hot.
If reading is:
a. 12 1/2 volts o r m ore, turn o ff e le c tr ic a l loads,
stop engine and p roceed to Step 7.
b. L e s s than 12 1/2 volts, p e rfo rm "D e lc o tro n Out­
put T e s t-V o ltm e te r M eth od."
V o lta g e S e ttin g
CHEVROLET TRUCK SERVICE MANUAL