Lighting - Auto Headlamps Switch ON/OFF Erratically
94 Automatic headlight switches on and off without reason
94 10 12
2016808/3
May 5, 2010
Supersedes Technical DIAGNOSIS AND REPAIR Group 94 number 08-35 dated November 13, 2008 for reasons listed below.
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Affected Vehicles
Condition
^ The customer may report that the headlight turns on or off early or late when the light switch is in the Auto position.
^ After replacing the rain-light sensor G397 or after replacing the windshield, the automatic headlight may turn on or off without change of ambient
brightness.
The headlights operate normally if the light switch is in the On or Off position.
Technical Background
Possible causes:
^ Window damaged or dirty in the area of the sensor.
^ After repairing the windshield, the sensor is fitted without adhesive pad.
^ The rain/light sensor coding for the window is wrong, or the wrong windshield was installed.
^ Wiring damaged (plug or contact loose).
Production Solution
No change.
Service
1. If the rain/light sensor or the windshield was not replaced or installed prior to the customer visit, visually check the windshield for dirt or scratches
in the area of the rain/light sensor.
2. If one of the components was replaced, focus your diagnosis on this part first.
a. Verify that the sensor is correctly installed. Check for bubbles and correct sensor position.
b. Verify the correct coding of the rain/light sensor to the windshield. Use the corresponding test plan of the 09 - Vehicle Electrical System
Control Module J519.
c. Check the connectors for correct fit.
d. Check the function of the light/rain sensor in the corresponding measured value block of J519 (depends on model). Use an incandescent source;
do not use fluorescent light. Position the light source as close as possible to the sensor.
Tip: The displayed value (signal condition) for brightness, 0 - 7 in the measured value block, has no influence on the conditions for switching the
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sensor on or off. This value is only for the Coming Leaving Home function. The sensitivity of the sensor cannot be altered.
3. If you determine that the rain/light sensor needs to be replaced, use the J519 test plan for replacing light/rain sensor G397 to ensure correct coding
and proper documentation after installation.
Warranty
Additional Information
All parts and service references provided in this TSB are subject to change and/or removal. Always check with your Parts Department and service
manuals for the latest information.
