GMC 1989 Light Duty Truck, Руководство по ремонту, Страница: 657 / 998

GENERATOR 6D2-5
Figure 9 — Regulator Connections
• Burned insu latio n appears as very d ark or
blackened wiring. A strong acid odor will be
apparent.
7. Terminal connectors for corrosion or breaks.
8. W indings on the stator for chipped insulation. If the
chipped area is small and the rest of the stator is OK,
repair the stator with insulating varnish.
9. Slip rings for scoring, wear or pitting.
• If the rings are dirty, clean with a 400 grain, or
finer, polishing cloth.
• Spin the rotor and hold the polishing cloth
against the slip rings until they are clean.
• If scored, worn, or pitted, true the rings in a lathe
to 0.05 mm (0.002 inch).
• Finish with 400 grain or finer polishing cloth.
Blow away all dust.
10. Rotor and stator w indings electrically as described
later under “ Electrical Tests” .
11. Generator housing for cracks, warping, or other dam ­
age.
12. If the regulator, brush assem bly or connector needs
replacing, it will have to be unsoldered from the other
two components. Use as little heat as possible to pro­
tect the regulator (figure 9).
ELECTRICAL TESTS
Except as stated, m ake the fo llo w in g tests w ith an
ohm m eter on the low range scale.
ROTOR FIELD WINDING CHECKS (Figure 10)
The rotor may be checked electrically with a 110-volt test
lamp or an ohmmeter.
Open Winding
To check for opens, connect the test lamp or ohm m eter to
each slip ring. If the lamp fails to light, or if the ohm m eter
reading is high (infinite), the w inding is open.
Figure 10— Checking the Rotor Field Windings
Grounded Winding
Connect a test lamp or ohm m eter from one slip ring to the
shaft. If the lamp lights, or if the reading is low, the rotor
winding is grounded.
Short Circuit or Resistance Check
The winding is checked for short circuits or excessive
resistance by connecting a battery and am m eter in series
with the edge of the two slip rings. Note the am m eter read­
ing and refer to “ Specifications” later in this section.
An amm eter reading above the specified value indicates
shorted windings. An alternate method is to check the
resistance of the field by connecting an ohm m eter to the
two slip rings. If the resistance reading is above the speci­
fied value the winding has excessive resistance; if below
the specified value the winding is shorted. The specified
resistance value can be determ ined by dividing the voltage
by the current.
Remember that the winding resistance and am m eter
rea din gs w ill va ry s lig h tly w ith w in d in g te m p e ra tu re
changes. If the rotor is not defective, but the generator fails
to supply rated output, the problem is in the rectifier bridge,
stator or regulator.
If the rotor fails any of the above checks, replace it.
STATOR CHECKS (Figure 11)
The stator may be checked with a 110-volt test lamp or
ohmmeter. If the ohm m eter reads low or if the lamp lights
when connected from any stator lead to bare metal on the
stator frame, the stator is grounded.