Lexus SC300 / Lexus SC400. Manual - part 692

SYSTEM CIRCUIT

OPERATION

When the ignition switch is turned ON, current from the battery flows from terminal L of the alternator through

the IC regulator to terminal E, causing the discharge warning light to light up.

Then when the engine is started, the voltage output increases as the alternator rpm increases. When the

voltage output becomes greater than the battery voltage, current for recharging flows from terminal B. Simulta-
neously, voltage at terminal L increases and the potential difference between battery and terminal L disappears,
causing the discharge warning light to go off. When the voltage output exceeds the regulator adjustment volt-
age, the transistor inside the IC regulator regulates the voltage so that the voltage from the alternator remains
constant.

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CHARGING SYSTEM

System Circuit, Operation

CH–3

PREPARATION

SST (SPECIAL SERVICE TOOLS)

09285–76010

Injection Pump
Camshaft Bearing
Cone Replacer

Rotor rear bearing

09286–46011

Injection Pump
Spline Shaft Puller

Rectifier end frame

09608–20012

Front Hub & Drive
Pinion Bearing Tool
Set

(09608–00030)

(Replacer)

Rotor front bearing

09820–00021

Alternator Rear
Bearing Puller

09820–00030

Alternator Rear
Bearing Replacer

09820–63010

Alternator Pulley Set
Nut Wrench Set

RECOMMENDED TOOLS

09082–00015

TOYOTA
Electrical Tester

09200–00010

Engine Adjust
Kit

EQUIPMENT

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Part Name

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Note

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Battery specific gravity gauge

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Battery

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Vernier caliper

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Rotor (Slip ring)

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Torque wrench

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CH–4

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CHARGING SYSTEM

Preperation

ON–VEHICLE INSPECTION

1. INSPECT BATTERY SPECIFIC GRAVITY AND

ELECTROLYTE LEVEL
(a)  Check the specific gravity of each cell.

Standard specific gravity:

1.27–1.29 when fully charged at 20

°

C (68

°

F)

If gravity is less than specification, charge the battery.
(b)  Check the electrolyte quantity of each cell.
If insufficient, refill with distilled (or purified) water.
HINT: Check the indicator as shown in the illustration.

2.  CHECK BATTERY TERMINALS, FUSIBLE LINKS AND

FUSES
(a) Check that the battery terminals are not loose or

corroded.

(b)  Check the fusible links and fuses for continuity.

H–fuse: ALT 

150A

AM1 100A

AM2 30A

M–fuse:  IG SW 40A

Fuse: IGN 

7.5A

ENGINE 7.5A

INJ 30A

3. 

INSPECT DRIVE BELT
HINT: A belt tensioner is used, so checking the belt tension
is not necessary.
(a)  Visually check the drive belt for excessive wear, frayed

cords, etc.

If necessary, replace the drive belt.
HINT:

•

Cracks on rib side of a drive belt are considered
acceptable. If the drive belt has chunks missing from the
ribs, it should be replaced.

•

The drive belt tension can be released by turning the
belt tensioner counterclockwise. The pulley bolt for the
belt tensioner has a left–hand thread.

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CHARGING SYSTEM

On–Vehicle Inspection

CH–5

(b)  Check the belt tensioner operation.

•

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.

•

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.

•

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:

•

When a new belt is installed, it should lie within area B.
If not, the drive belt is not correct.

•

After installing a belt, check that it fits properly in the
ribbed grooves.

•

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) Check 

that 

there 

is 

no abnormal 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