Chevrolet 70 1969 Series, Руководство по ремонту

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ENGINE ELECTRICAL 6Y-21
The generator is driven from ihe engine and
converts mechanical energy to electrical power.
The alternating current produced within the gen­
erator is rectified by six diodes installed in gen­
erator end frame and heat sink assembly. Direct
current is produced at output (BAT) terminal.
The regulator controls generator voltage out­
put by varying the current flow in field windings in
generator rotor assembly. No current regulating
device is required in the regulator used with A .C .
generator, since the generator has inherent cur­
rent regulation as long as the voltage is controlled.
Cut-out relay is not required with A .C . generating
system as the diodes will not conduct an electric
current in reverse direction; i.e., from battery to
ground through the generator.
PRECAUTIONS
N O T E : Observe the following precautions when
performing any service operations on the A .C .
generating system:
1. E L E C T R I C A L S Y S T E M IS N E G A T IV E
G R O U N D . Connecting the battery or a battery
charger with the positive terminal grounded will
endanger generator diodes and vehicle wiring by
high current flow. Burned wiring harnesses and
burned "Open'’ diodes will result.
2. Never operate the generator on an open
circuit (field terminal connected and output term­
inal disconnected). With no battery or electrical
load in the circuit (open circuit) the generator can
build up excessively high voltage. Be sure all con­
nections in the charging circuit are secure.
3. The generator cannot be polarized. Any
attempt to polarize the generator may result in
serious damage to charging system components.
4. When working near the generator or regu­
lator and before replacing electrical system com­
ponents, disconnect negative lead from the battery
to prevent accidental shorting at generator and
regulator terminals where battery voltage is
available.
5. Never replace the brown and white stripe
special resistance wire in harness connected to
ignition control switch unless it is of the same
material and of same length (approx. 60 inches
long). Generating system will not function without
this wire. W ire is identified on wiring diagrams
in Section 12 as 24-BN-WS-130. Resistance value
of wire is approximately -0-ohms, 6.25 watts.
I M P O R T A N T : Always locate and correct the
cause of a malfunction to prevent reoccurence.
ON-VEHICLE MAINTENANCE, TESTS, AN D ADJUSTMENTS
GENERATING SYSTEM
MAINTENANCE
By making the following inspection on the gen­
erating system at regular intervals, causes of
trouble may be located and corrected before they
progress to a point where they will seriously affect
the generating system performance.
1. Check generator drive belt tension and
adjust if necessary. See procedure later under
’’Generator Drive Belt Tension Adjustment.”
2. Check generator mounting and adjusting
arm bolts and tighten as necessary.
3. Check all electrical connections for tight­
ness and corrosion. Clean and tighten connections
as necessary. Be sure wiring insulation is in good
condition, and that all wiring is securely clipped
to prevent chafing the insulation.
4. With engine running, listen for noise and
check generator for vibration. If generator is noisy
or vibrates excessively, it should be removed for
inspection and repair.
5. Check battery electrolyte level and replen­
ish as necessary. Check specific gravity also.
GENERATOR DRIVE BELT
T E N S IO N A D J U S T M E N T
Because of the higher inertia and load capacity
of rotor used with A .C . generators, P R O P E R B E L T
T E N S IO N is more critical than o n D .C . generators.
All generators are pivot-base mounted with
the belt tension adjustment arm at the top. Use a
belt tension dial gauge to check tension on each
individual belt. If tension is not within 80-90 lbs.
(used belts) or 100-110 lbs. (new belts), loosen the
adjustment arm clamp bolt and move generator to
obtain recommended tension.
On a new vehicle, or after having installed
new belts, check tension twice in first 200 miles
of operation. When making adjustment, examine
belt(s) and replace if necessary.
A loose or broken drive belt will affect oper­
ation of generator. A drive belt that is too tight
will place excessive strain on bearings.
IM P O R T A N T : When replacing dual drive belts,
it is essential that the entire set be replaced at
same time. Belts are available in matched sets
only.
CHEVROLET SERIES 70-80 H EAVY DUTY TRUCK SH O P M A N U A L