1991 LEXUS SC300 alternator

(b) Check the belt tensioner operation.w Check that the belt tensioner moves downward
when the drive belt is pressed down at the points
indicated in the illustration with approx. 98 N ( 10
kgf, 22.0 lbf) of force.
w Check the alignment of the belt tensioner pulley to
make sure the drive belt has not slipped off the
pulley.
If necessary, replace the belt tensioner.
w Check that the arrow mark on the belt tensioner falls
within area A of the scale.
If it is outside area A, replace the drive belt.
HINT:
w When a new belt is installed, it should lie within area B.
If not, the drive belt is not correct.
w After installing a belt, check that it fits properly in the
ribbed grooves.
w Check by hand to confirm that the belt has not slipped
out of the groove on the bottom of the pulley.
4. REMOVE ENGINE UNDER COVER
5. VISUALLY CHECK ALTERNATOR WIRING AND LISTEN FOR ABNORMAL NOISES
(a) Check that the wiring is in good condition.
(b) C h e c k t h a t t h e r e i s n o a bnormal noise from the
alternator while the engine is running.
6. INSPECT CHARGE WARNING LIGHT CIRCUIT (a) Warm up the engine and then turn it off.
(b) Turn off all accessories.
(c) Turn the ignition switch ON. Check that the charge
warning light is lit.
(d) Start the engine. Check that the light goes off.
If the light does not go off as specified, troubleshoot the
charge light circuit.
CH±6
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CHARGING SYSTEM On±Vehicle Inspection
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7. INSPECT CHARGING CIRCUIT WITHOUT LOADHINT: If a battery/alternator tester is available, connect the
tester to the charging circuit as per manufacturer's instruc-
tions.
(a) If a tester is not available, connect a voltmeter andammeter to the charging circuit as follows:
w Disconnect the wire from terminal B of the
alternator and connect it to the negative (±) probe
of the ammeter.
w Connect the positive (+) probe of the ammeter to
terminal B of the alternator.
w Connect the positive (+) probe of the voltmeter to
terminal B of the alternator.
w Ground the negative (±) probe of the voltmeter.
(b) Check the charging circuit as follows:
With the engine running from idling to 2,000 rpm, check the
reading on the ammeter and voltmeter.
Standard amperage: 10 A or less
Standard voltage: 13.9±15.1 V at 25 5C (77 5F)
13.5±14.3 V at 115 5C (239 5F)
If the voltmeter reading is greater than standard voltage, re-
place the IC regulator.
If the voltmeter reading is less than standard voltage, check
the IC regulator and alternator as follows:
w Remove the engine under cover.
w With terminal F grounded, start the engine and
check the voltmeter reading of terminal B.
w If the voltmeter reading is greater than standard
voltage, replace the IC regulator.
w If the voltmeter reading is less than standard
voltage, check the alternator.
w Reinstall the engine under cover.
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CHARGING SYSTEM On±Vehicle InspectionCH±7
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8. INSPECT CHARGING CIRCUIT WITH LOAD(a) With the engine running at 2,000 rpm, turn on the highbeam headlights and place the heater blower switch at
ºHIº.
(b) Check the reading on the ammeter.
Standard amperage: 30 A or more
If the ammeter reading is less than standard amperage, re-
pair the alternator. (See page CH±9)
HINT: With the battery fully charged, the indication will some-
times be less than standard amperage.
9. REINSTALL ENGINE UNDER COVER
CH±8
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CHARGING SYSTEM On±Vehicle Inspection
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ALTERNATOR
COMPONENTS FOR REMOVAL AND
INSTALLATION
REMOVAL OF ALTERNATOR
1. DISCONNECT CABLE FROM NEGATIVE TERMINAL OFBATTERY
CAUTION: Work must be started after approx. 20 se-
conds or longer from the time the ignition switch is
turned to the ºLOCKº position and the negative (±) termi-
nal cable is disconnected from the battery.
2. REMOVE ENGINE UNDER COVER
3. REMOVE DRIVE BELT
Loosen the belt tension by turning the drive belt tensioner
counterclockwise, and remove the drive belt.
HINT: The pulley bolt for the belt tensioner has a left±hand
thread.
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CHARGING SYSTEM AlternatorCH±9
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4. REMOVE ALTERNATOR(a) Disconnect the alternator connector.
(b) Remove the cap and nut, and disconnect the alternatorwire.
(c) Remove the bolt, and disconnect the A/T oil cooler pipe bracket.
(d) Remove the nut and alternator.
COMPONENTS FOR DISASSEMBLY AND
ASSEMBLY
DISASSEMBLY OF ALTERNATOR
1. REMOVE REAR END COVER (a) Remove the nut and terminal insulator.
CH±10
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CHARGING SYSTEM Alternator
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(b) Remove the three nuts and end cover.
2. REMOVE BRUSH HOLDER AND IC REGULATOR (a) Remove the brush holder cover from the brush holder.
(b) Remove the five screws, brush holder and IC regulator.
3. REMOVE RECTIFIER HOLDER (a) Remove the four screws and rectifier holder.
(b) Remove the four rubber insulators.
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CHARGING SYSTEM AlternatorCH±11
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(c) Remove the seal plate.
4. REMOVE PULLEY (a) Hold SST (A) with a torque wrench, and tighten SST (B)clockwise to the specified torque.
SST 09820±63010
Torque: 39 N Vm (400 kgf Vcm, 29 ft Vlbf)
(b) Check that SST (A) is secured to the rotor shaft.
(c) As shown in the illustration, mount SST (C) in a vise, and
install the alternator to SST (C).
(d) To loosen the pulley nut, turn SST (A) in the direction
shown in the illustration.
NOTICE: To prevent damage to the rotor shaft, do not
loosen the pulley nut more than one±half of a turn.
(e) Remove the alternator from SST (C).
(f) Turn SST (B) and remove SST (A and B).
(g) Remove the pulley nut and pulley.
5. REMOVE RECTIFIER END FRAME (a) Remove the four mounting nuts.
(b) Using SST, remove the rectifier end frame.
SST 09286±46011
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CHARGING SYSTEM Alternator
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(c) Remove the alternator washer.
6. REMOVE ROTOR FROM DRIVE END FRAME
INSPECTION AND REPAIR OF
ALTERNATOR
Rotor
1. INSPECT ROTOR FOR OPEN CIRCUIT Using an ohmmeter, check that there is continuity between
the slip rings.
Standard resistance (Cold): 2.8±3.0

If there is no continuity, replace the rotor.
2. INSPECT ROTOR FOR GROUND Using an ohmmeter, check that there is no continuity be-
tween the slip ring and rotor.
If there is continuity, replace the rotor.
3. INSPECT SLIP RINGS (a) Check that the slip rings are not rough or scored.
If rough or scored, replace the rotor.
(b) Using a vernier caliper, measure the slip ring diameter.
Standard diameter: 14.2±14.4 mm
(0.559±0.567 in.)
Minimum diameter: 12.8 mm (0.504 in.)
If the diameter is less than minimum, replace the rotor.
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CHARGING SYSTEM AlternatorCH±13
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