Chevrolet 70 Series 1970, Service Manual

Page: 590 / 841

ENGINE ELECTRICAL 6Y-49
DIODES
I f *
ROLLER
s
BEARING
BEARING
WELL —
COVER
GREASE ' - t —
j
RESERVOIR
SEAL
STATIONARY FIELD COIL
(BRUSHLESS CONSTRUCTION)
Figure 2—Cross Section of 75-Amp. Integral Type Alternating Current Generator (Typical)
bridge and the diode trio from high voltage and
s u p p r e sse s radio n o ise.
The sp e c ia lly d esign ed output term inal is con­
n ected directly to the battery. The red output term ­
inal lea d m ust be connected to the battery p o sitiv e
term in a l.
NOTE: The hex head bolt on the output te r m ­
inal i s e le c tr ic a lly insulated; th erefo re, no volt­
a ge reading can be obtained by making te s t con­
n ection s at the hex head bolt.
A typical generating sy ste m u sed on v e h ic le s
equipped with the in tegral type alternating current
gen erator is sch em a tica lly illu stra ted in figu re 3.
NOTE: On v e h ic le s equipped with the Cummins
D ie s e l engine, a frequency sen sin g relay is fed
from the gen erator "R" term in a l. For inform ation
re la tiv e to th is r e la y , r e fe r to "Starter Autom atic
D isengagem ent and Lock Out" in "STARTING SYS­
TEM" p reviou sly.
PRECAUTIONS
O bserve the follow ing precautions when p e r ­
form ing s e r v ic e operations on the in tegral type
alternating current generating sy ste m . F ailu re to
o b serv e th ese p recau tion s may resu lt in se r io u s
dam age to the charging sy ste m .
1. E le c tr ic a l sy ste m i s negative ground. Con­
necting the battery o r battery charger w ith p o sitiv e
term in al grounded w ill endanger generator diodes
and v e h icle w iring by high current flow . Burned
w iring h a r n e sse s and burned "Open" diodes w ill
r e su lt.
2. N ever operate the generator on an open c ir ­
cu it (field term in al connected and output term inal
discon n ected ). With no battery or e le c tr ic a l load
in the circu it (open circu it) the generator can
build up e x c e s s iv e ly high voltage. B e su re a ll con­
nection s in the charging circu it a r e se c u r e .
3. The gen erator cannot be p o la rized . Any
Figure 3—Schematic Diagram of Integral Type AC Charging
Circuit (with 75-Amp. Generator) (Typical)
CHEVROIET SERIES 70-90 HEAVY DUTY TRUCK SHOP MANUAL