Lexus SC300 / Lexus SC400. Manual - part 285

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

7. 

INSPECT CHARGING CIRCUIT WITHOUT LOAD
HINT: 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 and

ammeter to the charging circuit as follows:

•

Disconnect the wire from terminal B of the
alternator and connect it to the negative (–) probe
of the ammeter.

•

Connect the positive (+) probe of the ammeter to
terminal B of the alternator.

•

Connect the positive (+) probe of the voltmeter to
terminal B of the alternator.

•

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

°

C (77

°

F)

13.5–14.3 V at 115

°

C (239

°

F)

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:

•

Remove the engine under cover.

•

With terminal F grounded, start the engine and
check the voltmeter reading of terminal B.

•

If the voltmeter reading is greater than standard
voltage, replace the IC regulator.

•

If the voltmeter reading is less than standard
voltage, check the alternator.

•

Reinstall the engine under cover.

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CHARGING SYSTEM

On–Vehicle Inspection

CH–7

8. 

INSPECT CHARGING CIRCUIT WITH LOAD
(a)  With the engine running at 2,000 rpm, turn on the high

beam headlights and place the heater blower switch at
”HI”.

(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