Diesel Data: Automotive Repair

Headlight (Hi-Beam) Circuit








LIGHTING (EXT): LIGHTING SYSTEM: Headlight (HI-BEAM) Circuit

Headlight (HI-BEAM) Circuit

DESCRIPTION

- When both of the following conditions are met, the high beam headlights will come on.

- The low beam headlights are turned on using either automatic light control or manual light control.
- The dimmer switch is in the HIGH position.

- The daytime running light relay dims the high beam headlights when operating them as daytime running lights.
- When the dimmer switch is turned to the HIGH FLASH position, the high beam headlights will come on.
HINT:
- If only a high beam headlight on one side does not illuminate, inspect the fuse, bulb, or wire harness related to the bulb.
- Before troubleshooting the high beam headlight control, check that the low beam headlights operate normally.

WIRING DIAGRAM





INSPECTION PROCEDURE

PROCEDURE

1. INSPECT HEADLIGHT DIMMER RELAY (DIM)




(a) Remove the headlight dimmer relay from the engine room relay block.
(b) Measure the resistance according to the value(s) in the table below.
Standard Resistance:






NG -- REPLACE HEADLIGHT DIMMER RELAY
OK -- Continue to next step.

2. CHECK HARNESS AND CONNECTOR (BATTERY - HEADLIGHT DIMMER RELAY)




(a) Measure the voltage according to the value(s) in the table below.
Standard Voltage:






NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR
OK -- Continue to next step.

3. CHECK HARNESS AND CONNECTOR (HEADLIGHT DIMMER RELAY - DAYTIME RUNNING LIGHT RELAY)
(a) Disconnect the E42 daytime running light relay connector.




(b) Measure the resistance according to the value(s) in the table below.
Standard Resistance:






NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR
OK -- Continue to next step.

4. CHECK HARNESS AND CONNECTOR (HEADLIGHT DIMMER RELAY - HEADLIGHT ASSEMBLY)
(a) Disconnect the A26 headlight assembly LH and A25 headlight assembly RH connector.




(b) Measure the resistance according to the value(s) in the table below.
Standard Resistance:






NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR
OK -- Continue to next step.

5. CHECK HARNESS AND CONNECTOR (HEADLIGHT ASSEMBLY - DAYTIME RUNNING LIGHT RELAY)
(a) Disconnect the E42 daytime running light relay connector.




(b) Measure the resistance according to the value(s) in the table below.
Standard Resistance:






NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR
OK -- PROCEED TO NEXT CIRCUIT INSPECTION SHOWN IN PROBLEM SYMPTOMS TABLE