Chevrolet 70 Series 1970, Service Manual

Page: 567 / 841

ENGINE ELECTRICAL 6Y-26
F 2 3 4
JUMPER
LEAD
WIRING HARNESS
CONNECTOR
tpms
/33
Figure 5 —Jum per Lead Connections fo r Testing
Indicator Lamp Circuit (TypicalI
GENERATOR ON-VEHICLE TEST
The following is a lis t of the m ost common
g e n e ra to r defects encountered:
1. Open o r sh o rte d g e n e rato r diodes.
2. Open, sh o rted , o r grounded s ta to r winding.
3. Open, sh o rted , o r grounded field winding.
4. Worn g e n e ra to r b ru sh e s.
5. E x cessiv e g e n e ra to r noise.
G e n erato r diodes and s ta to r windings should
be checked a s explained under "G enerator Output
T e s t" la t e r in th is section. If a defect is indicated
by th is te s t, rem ove the g e n e rato r and re p a ir.
G e n erato r field windings and b ru sh e s should
be checked a s outlined u n d er "Charging System
T rouble A nalysis C h a rt" la te r in th is sectio n . If
th is check indicates a defect in the field winding,
rem o v e the g e n e ra to r and re p a ir. R eplace worn
b ru sh e s a s explained under "G en erato r B ru sh R e­
placem en t" la te r in th is section.
£
=fr\
Jumper
Lead
WIRING HARNESS
CONNECTOR
TPM-9734
Figure 6 —Checking Indicator Lamp Wiring
E x ce ssiv e g e n e ra to r noise is usually the r e ­
su lt of one o r m o re of th e following:
1. B ru s h "Squeal" caused by a h a rd spot on
one of the b ru s h e s o r rough o r d irty slip rin g s.
To check fo r b ru sh "Squeal," rem ove g en e r­
a to r d riv e belt and spin g e n e ra to r d riv e pulley by
hand. Lift b ru sh e s off slip rin g s and spin d riv e
p ulley again. If no ise d isap p ea rs, clean and in spect
slip rin g s and re p la c e b ru sh e s if worn.
2. D ry o r rough b earin g s in g en e rato r end
fra m e .
IMPORTANT: Dry o r rough b earin g s may be
the re s u lt of o ver-tig hten ing g e n e rato r d riv e b e lt(s).
lo o se g e n e rato r m ountings, o r an unbalanced gen­
e r a to r fan o r pulley. Rem ove g e n e rato r and re p a ir.
3. A defective diode o r s ta to r re su ltin g in an
e le c tric a l unbalance.
To check fo r a defective diode o r s ta to r, p e r ­
fo rm "G enerator Output T e st" explained la te r in
th is sectio n . If a defect is indicated by th is te s t,
rem o ve g e n e ra to r and re p a ir.
GENERATOR CHARGE INDICATOR
LAMP CIRCUIT TEST
NOTE: R efe r to p ro c ed u re outlined in "C harg­
ing S ystem T rouble A nalysis C h art" la te r in th is
sec tio n to d eterm in e w hether som ething o th er than
a g e n e ra to r o r re g u la to r defect is ind icated b efo re
proceeding with th is te s t which applies to vehicles
equipped w ith a charg e in d icato r lam p.
1. Check the in d icato r lam p bulb which may be
burned out. Make s u re socket is fully engaged.
2. Check w iring connections a t junction.
3. Lift the re g u la to r te rm in a l latch slightly,
then pull connector fro m re g u la to r te rm in a ls.
CAUTION: Do not allow any leads to
contact a ground or "live" wire or term ­
inal except as directed. A heavy cloth,
taped in position below regulator term -
inals, will assist in preventing contact.
4. R efe rrin g to fig u re 5, in s e rt ju m p er lead
(J-9782-1) into #4 te rm in a l socket in h a rn e s s con­
n ec to r and ground the o th er end to re g u la to r b ase
a s illu s tra te d . M om entarily (not m ore than 10 s e c ­
onds) tu rn on ignition o r control sw itch. Ind icator
lam p should light. If not, check fo r open c irc u it in
w irin g between the jum per lead and sw itch, sw itch
and horn re la y , and to the b attery .
5. If in d icato r lam p com es on when #4 socket
In w iring h a rn e s s connector is grounded (fig. 5),
connect jum p er lead between w iring h a rn e ss con­
n e c to r te rm in a ls " F " and #4 a s shown in figu re 6.
T u rn ignition o r control sw itch on m om entarily.
a. If light com es on, and open c irc u it ex ists
within the re g u la to r. R efe r to re g u la to r te s ts la te r.
CHEVROLET SERIES 70-90 HEAVY DUTY TRUCK SHOP MANUAL