Chevrolet 70 1969 Series, Shop Manual

Page: 738 / 913

ENGINE ELECTRICAL 6Y-23
F ig u re 4 — R e p la c in g G e n e ra t o r P u lle y
OHMMETER
C H E C K I N G F O R
G R O U N D E D C IR C U IT
TPM-9758
F ig u re 5 — C h e c k in g Rotor fo r G r o u n d e d , S h o rte d , o r O p e n C ircu it U s in g
O h m m e t e r
C A U T IO N :
Do not use test lam ps of m ore than
12-volts. H igh e r voltage, such as 110-volt test
lam p, will im m ediately destroy a diode if prods
sh o u ld accidentally contact a d iode le a d w h e n
ch eck in g stator.
NOTE: Due to the low resistance of the stator
w indings it is not practical to check stator w ind­
ings for short circuits without laboratory equip­
ment; however, if all other electrical checks
show units to be in good condition, but genera­
tor fails to supply rated output, shorted stator
w indings are indicated.
1. Scrape epoxy coating from lead connections. Unsol­
der stator leads, using a minimum am ount of heat to
avoid damage to diodes to which stator leads are con­
nected.
NOTE: An alternate method is to cut stator
leads between coil and diodes. Leads must be
spliced after m aking checks.
2. Check for grounded stator windings by attaching one
lead from ohmm eter or test lamp to stator shell and
other lead to any one of the stator winding leads. If
the test lamp glows or if ohm m eter shows very low
reading, the windings are grounded.
3. To check for open circuits in stator windings, connect
ohmm eter leads or test lamp leads successively be­
tween the pairs of stator leads. If test lamp fails to
light, or if ohm m eter reading is very high (infinite),
an open circuit is indicated.
NOTE: If these checks show that the stator is
defective, a complete stator and shell assembly
must be installed when assembling generator.
Refer to "H eat Sink Replacement" covered later
under "R e p air" for procedure for assembling
heat sinks to stator shell.
DIODE CHECKS
Each diode in the two heat sinks (fig. 7) should be
checked individually for shorted or open condition when
overhauling generator.
Diodes can be checked using either a test lamp (12 volts
max.) or an ohmmeter.
C A U T IO N : D o not use a 110-volt test la m p to
test diodes.
NOTE: All diodes are identified in Figure 7.
O H M M E T E R
F ig u re 6 — C h e c k in g fo r G r o u n d e d or O p e n C ircu it in Sta to r
CHEVROLET SERIES 70-80 HEAVY DUTv TRUCK SH O P M A N U A L