Chevrolet 10 Series 1970 Service Manual page 402

ENGINE-ELECTRICAL 6Y-10
6, Do not attempt to p o la riz e the generator.
7. Do not disconnect lead at generator without fir s t
disconnecting battery ground cable.
Trou ble in the A .C . charging system w ill usually be
indicated by one or m ore o f the follow ing 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 battery
ces sive battery w ater usage).
4. E xcessive gen erator noise or vibration.
D escribed below are a s e r ie s of on -th e-veh icle quick
checks which are 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 tric a l system . Additional checks, ad­
justm ents and overhaul procedu res of these components
a re also d escrib ed in the
O perations S ec tio n " and
necessary.
STATIC CHECKS
B efo re making any e le c tr ic a l
follow in g static checks:
1. Check fo r loose fan belt.
2. Check fo r d efective
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 seriou sly
damage the charging system .
SYSTEM C O N D IT IO N TEST
(5 .5 " -6 .2 " DELCOTRON SYSTEMS)
Th is test is used to indicate the o v e ra ll condition of
the charging system (both good and d efective) and to
isolate the malfunctioning unit if the system is defective.
1. With ignition off, p e rfo rm
Checks outlined in this section. Then set hand brake
and shift transm ission into neutral.
(usually evidenced by e x ­
"C h a rgin g S ystem s-S ervice
should be r e fe r r e d to
checks, p e rfo rm
b attery. (R efer to B attery.)
the p resc rib ed Static
F ig . 5 c —A d ju st
2. Connect a voltm eter from
re la y to ground at regulator base.
CA UTIO N: Be_ sure m eter clip does not touch a
re s is to r or term inal 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
co rrection s (Indicator Lamp C ircu it T e s ts ) b efore
continuing.
M odels equipped
switch to " A C C "
a m m eter. If am m eter fa ils to read discharge, check
a m m eter circu it before continuing.
5. M odels equipped with Indicator Lamp: If lamp glows,
start the engine and run it at 1500 rpm or above.
as
Check indicator lamp. If lamp fa ils to go out, p e r­
form appropriate
Lamp C ircu it T e s t) before continuing.
M odels equipped with A m m eter: If am m eter reads
discharge, start the engine and observe am m eter. If
m eter fa ils to m ove toward charge (from origin a l
position), p erfo rm appropriate test and correctio n s
the
(F ie ld C ircu it T e s ts ) before continuing.
NOTE: A t this point a fie ld circu it has been
established and any other problem
gen erator or regu lator.
6. Turn on high-beam headlights and heater blow er
m otor to high speed,
rpm (fo r a few minutes, if n ecessa ry) and read the
voltage on m eter.
NOTE: Voltage 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 or m ore, turn o ff e le c tric a l loads,
stop engine and proceed to Step 7.
b. L e s s than 12 1/2 volts, p erfo rm "D e lc o tro n Out­
put T e s t-V o ltm e te r M ethod."
V o lta g e S e ttin g
junction block on horn
with A m m eter: Turn ignition
with an a ccesso ry on and check
test and correction s (Indicator
w ill lie in
run engine at or above 1500
CHEVROLET TRUCK SERVICE MANUAL