Chevrolet 10 Series 1970 Service Manual page 408

ENGINE-ELECTRICAL 6Y-16
F ig . 15c—F ie ld Resistance Tests
If the ohm m eter reads low the winding is shorted
5 .
o r grounded.
NOTE: The sp ecified resistan ce value can be
determ ined by dividing the voltage by the cu r­
rent given in specification s. Since the reading
is taken through the adapter, leads, brushes and
slip rin gs, the ohm m eter reading on a good fie ld
winding w ill be sligh tly higher than the sp ecified
value. T h is is true because the sp ecified value
is fo r an ohm m eter reading d ire c tly a c ro s s the
slip rin gs.
6. Disconnect ohm m eter
ground strap.
Testing Circuit Resistance
E x cessive resistan ce in the sensing circu it, consisting
o f a ll fie ld leads and the regu lator, can cause an o v e r ­
charged battery.
1. Turn on switch but do not start engine.
2. A ltern a tely connect a voltm e te r as shown in P a r t 1
and P a r t 2 in F igu re 16c.
3. If the two v o ltm e te r readings total m ore than .3
volt, check fo r e x c e s s iv e resistance in fie ld circu it
leads. If these leads a re satisfa ctory, the fie ld rela y
contacts may have e x c e s s iv e resistan ce. In this case
replace the relay.
V o ltage Setting Adjustm ent
A voltage setting not ta ilo re d to m eet v e h icle r e q u ir e ­
ments can result in an undercharged or an overch arged
battery. T o adjust the voltage setting, proceed as follow s:
1. Connect a v o ltm e te r to the adapter as shown in
Figu re 14c, P a r t 1.
2. Connect an am m eter in the c ircu it at the " B A T "
term in al on the gen erator.
a n d reconnect the battery
D IS C O N N E C T
FROM
REGULATOR
W IR IN G
H A R N E S S
F ig . 16c—C ir c u it Resistance Test
3. Turn a ll a c c e s s o rie s off.
4. Operate gen erator at approxim ately 3000 rpm (1500-
2000 engine rpm ).
5. The gen erator output should be at lea st 10 am peres
below the rated gen erator output fo r this check.
Exam ple: If gen erator rated output is 130 amps, the
regu lator is lim itin g voltage i f am perage
o r les s .
6. T o adjust voltage setting, rem ove pipe plug and
turn slotted adjusting button inside regu lator.
NOTE: A fte r two notches in each direction ,
there is a p ositive stop.
70 F or an undercharged battery, ra ise voltage setting
by turning one notch and then check fo r an im proved
F ig . 17c—P u lle y Removal
TO G R O U N D
O N GENERATOR
C = ^
OHMMETER
OHMMETER
is 120
CHEVROLET TRUCK SERVICE MANUAL