Chevrolet DB90 Series, Service Manual

Page: 139 / 242

Sec. 6Y -133
A. C. GENERATING SYSTEM (NON-INTEGRAL TYPE)
battery should be checked for co rre ct sp ecific
gravity. Then generator drive belt should be check­
ed for proper ten sion , and wiring should be v isu a l­
ly inspected for lo o se or corroded connections.
NOTE: On som e v e h ic le s equipped with the
1116374 regulator, the No. 4 regulator term inal is
not used.
A typical circu it with an indicator lamp is
shown in figure 15, how ever, the sam e te st con­
nection s are made on v e h ic le s equipped with the
am m eter type charge indicator.
1. D isconnect w iring from generator "BAT”
term in al and w iring h arn ess connector from g en er­
ator "F” and "R” term in a ls. Make connections as
shown in View A, figu re 15.
NOTE: A m m eter is connected between g en er­
ator "BAT” term in al and the lead disconnected
from generator "BAT" term in al. V oltm eter is con­
nected between gen erator "BAT" term inal and
ground, and jumper lead is connected between "R"
and "F" term inal on generator.
2. R efer to gen erator sp ecifica tio n s at end of
th is sectio n , then sta rt engine and operate at s p e c i­
fied speed. Turn on a c c e s s o r ie s or connect a ca r ­
bon p ile a c r o s s the battery a s required to obtain
sp ecified voltage and o b serve current output.
IMPORTANT: Do not perm it voltage to exceed
16 v o lts.
a. If current output is low er than sp ecified ,
rep air or rep lace the generator.
NOTE: If generator failu re was caused by a
d efective stator or diode, no further checks are
required on the system ; however, if generator
fa ilu re was caused by a d efective field winding,
the follow ing checks must be made to locate p o s ­
sib le damage to the regulator.
b. If current output is within lim its liste d in
"Specifications" the generator is sa tisfa cto ry .
3. Rem ove jumper lead, am m eter, and v o lt­
m eter from generator and connect wiring h arn ess
connector to generator "F" and ”R ” term in als and
connect lead to "BAT" term inal on generator.
4. Make connections a s shown in View B , Part
1, figu re 15. Slide te st prods into regulator con­
nector body to make connections and do not leave
jumper lead connected longer than fiv e m inutes.
NOTE: V oltm eter p o sitiv e lead is connected to
battery p o sitiv e p ost and voltm eter negative lead
is connected to No. 3 term inal on regulator. Jum p­
er lead is connected between No. 2andN o. 3 te r m ­
in als on the regulator.
a. Turn ignition or control sw itch on and r e ­
cord the voltage drop.
b. Make connections as shown in View B , Part
2, figu re 15, and record the voltage drop.
NOTE: V oltm eter p o sitiv e lead is connected
to regulator mounting bolt and voltm eter negative
lead is connected to battery negative post with
Figure 16—A d ju stin g V olta g e Setting (Typical)
jum per lead connected betw een No. 2 and N o.3
term in a ls on the regulator.
c. Add voltage in Step a. to voltage in Step b.
above. If total voltage (a. + b.) is g rea ter than .25
volt, check sy ste m w iring for high r e sista n c e .
d. If total voltage in Step c. is below .25 volt,
rem ove jumper lead connected between regulator
No. 2 term in al and No. 3 term inal and connect v o lt­
m eter between No. 3 term in al on regulator and
ground a s shown in View C, figure 15.
e. Start engine and run at approxim ately 1275
rpm for 15 m inutes. L eave cover on regulator.
P la c e a therm om eter %-inch from regulator cover
and com pare voltage with "Specifications" given in
"Tem perature V oltage C hart” at end of this sectio n .
f. If voltage is not within sp ecified lim its, r e ­
m ove a c c e s s plug from regulator cover and note
p osition of p la stic sc r e w slo t beneath the plug. The
slo t w ill be aligned with one of the division lin e s
ca st on the cover. For each line the slo t has been
moved toward the "+" mark, add 0.3 volt to p r e v i­
ous sp ecified range for proper voltage lim its, and
for each d ivision the slo t has been moved toward
mark, subtract 0.3 volt from p reviou s s p e c i­
fied range for the proper sp ecified voltage lim its.
g. If actual regulating voltage is not within the
voltage range sp ecified for m easured ambient
tem perature, rep air or rep lace the regulator.
h. If actual regulating voltage as checked, is
within the voltage range sp ecified for the m easured
am bient tem perature, the charging sy ste m o p er­
ation is satisfactory; how ever, the regulator v o lt­
age setting m ust be changed to m eet battery charg­
ing req u irem en ts.
5. To adjust voltage regulator settin g, rem ove
a c c e s s plug from regulator cover and u se a thin,
flat-b lad ed instrum ent to turn the slo tted adjuster
(fig. 16).
NOTE: A fter two notches in each direction
there is a p o sitiv e stop.
a. To r a is e the voltage settin g, turn slotted
adjuster one notch (clock w ise), then check for an
im proved battery condition a fter a s e r v ic e period
of reasonable length.
b. To low er the voltage settin g, turn slotted
CHEVROLET SERIES 70-90 HEAVY DUTY TRUCK SHOP MANUAL SUPPLEMENT