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Greetings all, 2004 645ci. The low beam cap came off of passenger side headlight some time ago and moisture collected in housing. There is a green light blinking on headlight control switch and the neither headlight will auto-level. I have tested the bulb and ignitor, no problems. Im thinking the ballast got wet and died on me but, if the headlight control module died as well. Why would it effect the drivers side. Also, whats the difference between the control module on the side of the headlight and, the one in the footwell???.....PLEASE HELP.
 

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Greetings all, 2004 645ci. The low beam cap came off of passenger side headlight some time ago and moisture collected in housing. There is a green light blinking on headlight control switch and the neither headlight will auto-level. I have tested the bulb and ignitor, no problems. Im thinking the ballast got wet and died on me but, if the headlight control module died as well. Why would it effect the drivers side. Also, whats the difference between the control module on the side of the headlight and, the one in the footwell???.....PLEASE HELP.
The AHL is the module that controls the side to side movement. The bottom module controls the up & down movement of the light. There are not any internal parts for the light assembly, so you would have to remove the lens to repair the low beam cap. I would suggest to remove the bumper cover & inspect the modules for moisture. To save money you can buy used ones off of Ebay. Have some type of BMW software would really help a lot for troubleshooting your problems.
 

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Greetings all, 2004 645ci. The low beam cap came off of passenger side headlight some time ago and moisture collected in housing. There is a green light blinking on headlight control switch and the neither headlight will auto-level. I have tested the bulb and ignitor, no problems. Im thinking the ballast got wet and died on me but, if the headlight control module died as well. Why would it effect the drivers side. Also, whats the difference between the control module on the side of the headlight and, the one in the footwell???.....PLEASE HELP.
Unfortunately, I know too much about headlights now...lol...after diagnosing and eventually replacing my own.

The light has two modules on the outside, bottom one is the ballast/igniter for the Xenon bulb, the smaller one to the side (has a black plastic cover rather than metal), is the controller for the AHL motors.

As HerbP suggested, pull off the bumper and then you have access to the headlights. Swap the AHL module to the other headlight and see if it works in that one. If not, the module is dead (best case scenario).

If it *does* work on the other side, then likely the AHL stepper motors are defective and you would need a new headlight as I don't believe any parts inside are replaceable - unless you are ambitious enough to open the headlight.

Good luck!
 
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