e. Electrical Tests, Alternator Disassembled.
following manner. Connect the negative lead of an
(1) Stator disconnector.
ohmmeter to test point one and touch the positive lead to
Slide the three
terminals 4, 5 and 6. A high resistance reading should
insulating sleeves away from the splices and unsolder
be obtained. If a low resistance reading is obtained, the
the splices to disconnect the stator from the rectifiers (23
diode is shorted and must be replaced. See figure 3-3.
and 24).
(b) Rotor tests are performed with an
(2) Stator ground test. Connect a test light
ohmmeter and consist of a resistance check and ground
from each stator lead to the stator core or frame of the
test. Rotor coil resistance should be 7.0 to 7.8 ohms and
alternator. If the bulb lights, the stator is grounded and
is measured by connecting the ohmmeter across the two
must be replaced. (See stator replacement).
slip rings. If the resistance is not within the above
specifications, the rotor coil is defective. Check for
light between each phase of the stator. If the bulb fails to
grounds by connecting the ohmmeter between either slip
light, the stator is open and should be replaced. (See
ring and the shaft. No reading should be obtained. If a
stator replacement).
reading is obtained, the rotor coil is grounded. If the coil
(4) Rectifier tests-positive heat sink. The
is defective or slip rings are badly worn it will be
positive heat sink is insulated from the housing by means
necessary to replace the complete rotor assembly.
of a rubber insulator under its base and fiber washers
f. Voltage Regulator. If preceeding test indicate
and bushings around the retaining screws and stud.
that all components are working satisfactorily a defective
Carefully check for broken or missing insulators which
regulator is indicated and a new one should be installed.
could cause the positive heat sink to ground to the
Due to special testing equipment required repair of this
housing. The diodes may now be checked in the
regulator is not recommended.
following manner. Connect the negative lead of an
g. Diode Replacement. If electrical tests indicate
ohmmeter to test point two and touch the positive lead of
one or more defective diodes, the following procedure
the ohmmeter to diode terminals, 1, 2, and 3. A low
should be followed. Unsolder the lead from the defective
resistance reading should be obtained. Reverse the
diode and push the lead aside. With a sharp knife or ice
ohmmeter leads connecting the positive lead to test point
pick, carefully remove the RTV rubber sealant from
two and touch the negative lead to the diode terminals 1,
around the diode, and unscrew the diode using a suitable
2, and 3. A high resistance reading should be obtained.
11/16 socket wrench.
After the diode has been
If a low resistance reading is obtained, the diode is
removed, check the mounting surface of the heat sink for
shorted and must be replaced. See figure 3-3.
burrs or foreign matter which would prevent the new
diode from seating properly. It is very important that the
diode seat firmly against the heat sink to insure proper
heat transfer as well as electrical contact.
CAUTION
Diodes used in the negative
(grounded) heat sink differ from
those
used
in
the
positive
(ungrounded) heat sink. If they are
interchanged, serious damage will
result. Consult figure 3-4 to insure
proper diode identification and
position. Insert the proper diode,
tighten to 20-25 inch pounds torque
and reconnect the lead.
When
resoldering, do not use excessive
heat which could damage the diode.
Reseal the diode against moisture.
Figure 3-3. Carrier engine rectifier testing-(Model 2385).
(5) Rectifier Tests-Negative Heat Sink.
(a) The negative heat sink is grounded
to the housing by means of its mounting screws 3-8 and
stud. Be sure that these screws are clean and tight so
that the negative heat sink makes good contact with the
housing. The diodes may now. be checked in the
3-8
