GMC 4000 Series Service Manual page 433

Sec. 6Y
Page 422
A/C GENERATING SYSTEM
A ir G a p (Check
W ith Points
Just Tou ch ing)
.0 1 5 Inch
Feeler G a u g e
Figure 19— Adjusting Field Relay Air G ap
the upper and lower contacts. Instructions for mak­
ing final setting are explained previously. See
"Regulator Voltage Test (On Vehicle)."
FIELD RELAY UNIT CHECK
NOTE: Check closing voltage as explained
under "Regulator Unit Field Relay Test - On Ve­
hicle" in "ALTERNATING CURRENT GENERAT­
ING SYSTEM" section previously.
CHECKING AND ADJUSTING AIR GAP
Referring to figure 19, insert a 0.015-inch
GENERAL
The full transistor regulator is used on models
equipped with the 62-amp generator as shown in
"Model Application Chart" previously.
The regulator is composed of transistors,
diodes, capacitors and resistors which form a
completely static electrical unit containing no
moving parts.
The function of the regulator is to limit volt­
age to a given value. The voltage at which the gen­
erator is limited is determined by the regulator
adjustment which, when adjusted, remains prac­
tically unchanged. Refer to "Regulator Adjustment"
later in this section.
IMPORTANT: The field wire terminal must
not be grounded or flashed when regulator is con­
nected into circuit as instant damage to transistors
will result.
OPERATING PRINCIPLES
In the circuit illustrated in figure 2 in "Gen­
erating System General Description" section, when
G M C S E R V I C E M A N U A L
Su p p o rt Sp rin g
(Bend if N e cessary)
FULL TRANSISTOR REGULATOR
(1116374 A N D 1116378)
.0 3 0 Inch
Feeler G a u g e
Figure 2 0 — Adjusting Field Relay Contact Points
feeler gauge between the armature and core and
exert just enough pressure on the armature to a l­
low it to touch the gauge. The contact set should
just close at this time, adjust by bending the flat
contact support spring.
CHECKING AND ADJUSTING
CONTACT POINT GAP
Referring to figure 20, insert an 0.030-inch
feeler gauge between the contact points with the
armature in its normal rest position.
The point opening can be adjusted, if neces­
sary, by bending the relay heel iron.
ignition switch is closed and engine is not running,
the ammeter will show a discharged condition of
the indicator lamp will "light," to indicate the
generator is not charging. The current flow can be
traced from the battery to the "BAT" terminal on
the ignition switch, through the indicator lamp and
resistor, then to No. 2 or 4 terminal on the regu­
lator. From here it continues to flow through tran­
sistor TR-1 to "F" terminal on the regulator and
on through the generator field winding to ground,
completing the circuit back to the battery.
When the engine is started and generator be­
gins to operate, A.C. voltages are induced in the
generator stator windings. These voltages are
changed or rectified to D.C. voltage which appears
at the output, or "BAT" terminal on the generator.
The generator then supplies current to charge the
battery and operate vehicle accessories.
On 62-amp generating system s equipped with
the 1116374 transistorized regulator, system volt­
age is im pressed through regulator #2 terminal and
through field relay winding causing relay contacts
to close.
On 62-amp generating system s equipped with
A rm a tu re Stop
(B end if N e ce ssary )