GMC 4000 Series Service Manual page 428

Figure 10— Testing Field Relay Closing Voltage
(Two-Unit Type Regulator) (Typical)
a. Connect a 100-150 ohm variable resistor
and a voltmeter to the adapter as shown.
NOTE: If the 0-50 ohms variable resistor unit
(J-21260) is used, it will be necessary to add a 15
and a 115 ohm resistor in same series to provide
required resistance.
b. Turn resistor to the open or "full r e sist­
ance" position. Leave ignition or control switch off.
c. Slowly decrease resistance and note the
closing voltage. Voltage should be 1.5 to 3.2 volts
on 1119515 or 3.8 to 7.2 volts on 1119507. If n eces­
sary, adjust by bending the armature support heel
iron.
REGULATOR VOLTAGE TEST
(ON VEHICLE)
The voltage at which the regulator operates
varies with changes in regulator ambient temper­
ature which is the temperature of air at a distance
of %-inch from the regulator.
GENERATING SYSTEM WITH
TWO-UNIT TYPE REGULATOR
1. Refer to figure 11 which shows all test
equipment connected into system . Figure 12 shows
use of special adapter and jumper lead at regulator.
2. Connect an ammeter and a %-ohm resistor
with a rating of 25 watts or more in series in
the circuit at the "BAT" terminal on the generator
(fig. 11). In the event the battery is discharged, the
%-ohm resistor will limit the generator output to
10 amperes or le ss which is required, when check­
ing and adjusting the voltage setting.
3. Install special adapter as shown in figure
11. Use a 25 ohm 25 watt variable resistor in
ser ie s with the generator field windings atthereg-
G M C S E R V I C E M A N U A L
ulator "F" terminal, and connect a jumper lead
from the #3 adapter lead to the generator "BAT"
terminal as shown. Connect a voltmeter from the
#3 adapter lead to ground as shown. Turn the re­
sistor to the closed or "no resistance" position.
establish operating temperature. With all a cc ess­
ories and lights off, start and operate engine for
15 minutes at 1500 engine rpm.
RESISTANCE" position.
connector momentarily, then reconnect lead.
A/C GENERATING SYSTEM
Figure 1 7 — Connections for Testing Regulator
Voltage Setting (Two-Unit Type Regulator)
4. Secure a thermometer close to regulator to
5. After warm-up, cycle generator as follows:
a. Turn variable resistor to "OFF" or "FULL
b. Disconnect lead at #4 terminal of harness
Figure 1 2 — Testing Voltage Setting
(Tw o-Unit Type Regulator)
Sec. 6Y
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