Toyota 4Runner: Operating Light Control Rheostat does not Change Light Brightness

Toyota 4Runner Service Manual / Vehicle Interior / Meter / Gauge / Display / Meter / Gauge System / Operating Light Control Rheostat does not Change Light Brightness

DESCRIPTION

When the light control rheostat dial is turned upward, the combination meter and vehicle interior illumination will become brighter. When the light control rheostat dial is turned downward, the combination meter and vehicle illumination will dim.

WIRING DIAGRAM

PROCEDURE

1.	READ VALUE USING TECHSTREAM (LIGHT CONTROL RHEOSTAT)

(a) Operate the Techstream according to the display and select the Data List (See page ).

Combination Meter

Tester Display	Measurement Item/Range	Normal Condition	Diagnostic Note
Tail Cancel SW*	TAIL cancel switch condition/ON or OFF	ON: TAIL cancel switch on OFF: TAIL cancel switch off	-
Rheostat value	Light control rheostat switch input/Min.: 0, Max.: 100	Light control rheostat switch fully turned downward (0) → fully turned upward (100)	Unit: %

Tester Display

Measurement Item/Range

Normal Condition

Diagnostic Note

Tail Cancel SW*

TAIL cancel switch condition/ON or OFF

ON: TAIL cancel switch on

OFF: TAIL cancel switch off

Rheostat value

Light control rheostat switch input/Min.: 0, Max.: 100

Light control rheostat switch fully turned downward (0) → fully turned upward (100)

Unit: %

*: w/ TAIL Cancel Switch

OK:

Light brightness can be changed within specified range by manual operation.

REPLACE COMBINATION METER ASSEMBLY

2.	INSPECT LIGHT CONTROL RHEOSTAT

w/o TAIL Cancel Switch:

(a) Inspect the light control rheostat.

(1) Remove the light control rheostat (See page ).

(2) Measure the resistance according to the table below.

Standard Resistance:

Tester Connection	Switch Condition	Specified Condition
7 (T) - 1 (E)	Always	8 to 12 kΩ
3 (RV) - 1 (E)	Light control rheostat fully turned upward → fully turned downward	8 to 12 kΩ → Below 50 Ω

w/ TAIL Cancel Switch:

(b) Inspect the light control rheostat.

(1) Remove the light control rheostat (See page ).

(2) Measure the resistance according to the table below.

Standard Resistance:

Tester Connection	Switch Condition	Specified Condition
7 (T) - 5 (TC)	TAIL cancel switch off → on	1 MΩ or higher → Below 1 Ω
7 (T) - 1 (E)	Always	8 to 12 kΩ
3 (RV) - 1 (E)	Light control rheostat fully turned upward → fully turned downward	8 to 12 kΩ → Below 50 Ω

REPLACE LIGHT CONTROL RHEOSTAT

3.	CHECK HARNESS AND CONNECTOR (COMBINATION METER - LIGHT CONTROL RHEOSTAT)

(a) Disconnect the F14 meter connector.

(b) Disconnect the F5 rheostat connector.

Standard Resistance:

Tester Connection	Condition	Specified Condition
F14-36 (TC) - F5-5 (TC)*	Always	Below 1 Ω
F14-37 (RHIG) - F5-7 (T)
F14-38 (TR) - F5-3 (RV)
F14-39 (E2) - F5-1 (E)

*: w/ TAIL Cancel Switch

REPAIR OR REPLACE HARNESS OR CONNECTOR

4.	REPLACE COMBINATION METER ASSEMBLY

(a) Replace the combination meter assembly with a new or normally functioning one. Perform an operation inspection.

OK:

Combination meter assembly operates normally.

END

GO TO LIGHTING SYSTEM

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