Chevrolet DB90 Series, Руководство по обслуживанию

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Sec. 6Y-143
A. C. GENERATING SYSTEM (NON-INTEGRAL TYPE)
IMPORTANT: R eplacing any of the previous
com ponents should not affect the voltage settin g.
If any of the follow ing com ponents require r e ­
placem ent, adjust the voltage settin g a s explained
under "Regulator Voltage Adjustment" la ter in this
sec tio n .
ZENER DIODE
(PART 16, Fig. 28)
If both readings are infinite or if both read ­
ings are identical, rep lace the diode.
THERMISTOR
(PART 17, F ig. 28)
Connect the ohm m eter as shown in figure 25.
If the reading is infinite, the th erm istor is open
and should be replaced.
VOLTAGE DIVIDER RESISTOR R - l
(PART 18, F ig. 28)
If one reading is infinite o r nearly infinite,
or if both readings are infinite or nearly infinite
the r e s is to r is open and should be replaced.
VOLTAGE DIVIDER RESISTOR R -3
(PART 19, F ig. 28)
If one reading is infinite or nearly infinite, or
if both readings a re infinite or nearly infinite, the
r e s is to r is open and should be replaced.
POTENTIOMETER
(PART 20 AND 20A, F ig. 28)
If one reading is infinite or nearly infinite
when connected a s shown in P art 20, the potenti­
om eter is open. If one reading is infinite or nearly
infinite when connected a s shown in P art 20A, the
p otentiom eter is open.
NOTE: When in stallin g a new potentiom eter,
lo ca te the adjusting le v e r in a v ertica l position
(fig. 26), turn the potentiom eter r e sista n ce adjust­
ment to the middle position, then u se a soldering
iron to m elt the le v e r into potentiom eter.
REGULATOR UNIT RELAY
(MODEL 1116374 OR 1116378)
The relay unit may be checked as follow s.
R efer to figu re 31 for te s t connections.
1. Connect an ohm m eter a c r o ss term in a ls as
shown in figure 31. An infinite reading indicates an
open shunt c o il which w ill require replacing the
r ela y .
2. To check closin g voltage, connect a battery,
50 ohm variab le r e s is to r and voltm eter into circu it
a s shown in figure 31. Slowly d ecrea se r e sista n c e
and note voltage at which relay points c lo s e . If
voltage at which points c lo se is not within lim its
lis te d in "Specifications" rep lace the relay.
HEAT ADJUSTING
INSULATOR SINK LEVER INSULATOR
Figure
3 4 —Top Side o f Panel
Board Assembly
REGULATOR VOLTAGE ADJUSTMENT
(MODEL 1116374 OR 1116378)
A fter replacing any com ponents in Part 16
through 20 p rev io u sly , regulator voltage must be
calibrated to com pensate for variations in operat­
ing c h a r a c te r istics between com ponents. The v o lt­
age setting m ust be p r e c ise to maintain sy ste m
voltage within lim its liste d in "Specifications" at
end of th is sectio n .
1. C arefully apply soldering iron to le v e r of
p otentiom eter at point shown in figure 26, then d is ­
connect le v e r from opposite sid e of panel board
w hile heat is being applied.
2. U se a sm a ll screw d riv er to position center
portion of potentiom eter in m iddle p osition.
3. With regulator a ssem b led , except for bot­
tom cover plate and potentiom eter le v e r , connect
the generator, regulator, and battery into circu it.
Connect a te st am m eter between battery p ost and
battery lead.
4. D rive generator at 6,000 rpm with an e le c ­
tr ic load of 15 to 20 am p eres.
NOTE: A carbon p ile r e s is to r may be required
a c r o s s battery p osts to obtain required am perage.
5. Connect a te s t voltm eter between regulator
N o. 3 term inal and ground.
6. Adjust center p osition of potentiom eter to
obtain a voltage settin g of 14.4 v o lts at regu lator.
V oltage w ill require readjustm ent every fiv e m in­
u tes until voltage b ecom es stab le. N orm ally 15 to
20 minutes w ill be required fo r this p r o c e s s .
NOTE: T his voltage is based on the assu m p ­
tion that regulator is being se t on a te st bench at
CHEVROLET SERIES 70-90 HEAVY DUTY TRUCK SHOP MANUAL SUPPLEMENT