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      11-25-2012, 01:10 PM   #6
Bill B.
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Drives: '12 135i, '13 X135i '15 S1000R
Join Date: Sep 2011
Location: Cary, NC

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Originally Posted by M3to335 View Post
No aftermarket parts are on this car. If condensation made it's way in (very possible) then what specifically is the failure point and how do I confirm weather or not it's failed. Only the passanger side was opened and corner bulb replaced. You'd think the drivers side would still funtion. Unless it's wired in series?
Since you have a warning light on, the quickest way to identify the failure point would be with a code reader.

I have heard the stepper motors themselves are unreliable, but I have not seen a separate part number for them. Sometimes they become detached from the ball joint, but that usually wouldn't throw a code.

If a motor has failed, and a code has been thrown, I would think the controller would be mart enough not to try and drive EITHER motor.

There is a separate ACL module that does have a part number, that is most likely the motor controller. Other than reading the code, I don't know of a simple way to determine if it is the controller or the stepper.

Unfortunately, I have not heard anyone having successfully repaired this feature without replacing the entire headlight assembly.