Headlight gremlin
02-15-2022, 05:28 PM
#1
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Thread Starter
Headlight gremlin
2012 E350 Cabrio w/Bi-Xenon Headlights
Driver's side headlight fails unpredictably, sometimes when the car is first started but usually after 5 to 10 minutes, followed by "Adaptive Headlamp Assist Inoperative" message. The problem clears after the car sits for a while.
My first step was to swap the D1S headlamp with the passenger side. The problem stayed at the driver's side.
My next step was to replace the driver's side control unit and have the dealer program it while it was in the shop for the airbag recall and a seat recline issue.
I am observing two failure modes:
Failure mode 1: The headlight just goes dead. Nothing happens when I go from auto to manual or pull the multifunction switch for bright lights. The stepper motor does not energize and lamp does not come on.
Failure mode 2: The lamp goes out but when going from auto to manual it will flash momentarily and the stepper motor energizes. Same thing when the multifunction switch is pulled for bright lights. It generally operates normally after the car sits for a while.
Before I take it back to the dealer for further diagnostics, does anyone have any advice?.
I have inspected the wiring around and inside the headlight assembly and everything looks pristine. I have read horror stories of dealers recommending SAM replacement when the root cause was simple and inexpensive.
Thanks much.
Driver's side headlight fails unpredictably, sometimes when the car is first started but usually after 5 to 10 minutes, followed by "Adaptive Headlamp Assist Inoperative" message. The problem clears after the car sits for a while.
My first step was to swap the D1S headlamp with the passenger side. The problem stayed at the driver's side.
My next step was to replace the driver's side control unit and have the dealer program it while it was in the shop for the airbag recall and a seat recline issue.
I am observing two failure modes:
Failure mode 1: The headlight just goes dead. Nothing happens when I go from auto to manual or pull the multifunction switch for bright lights. The stepper motor does not energize and lamp does not come on.
Failure mode 2: The lamp goes out but when going from auto to manual it will flash momentarily and the stepper motor energizes. Same thing when the multifunction switch is pulled for bright lights. It generally operates normally after the car sits for a while.
Before I take it back to the dealer for further diagnostics, does anyone have any advice?.
I have inspected the wiring around and inside the headlight assembly and everything looks pristine. I have read horror stories of dealers recommending SAM replacement when the root cause was simple and inexpensive.
Thanks much.
Last edited by mlonas; 02-18-2022 at 12:24 PM. Reason: additional information
03-28-2022, 09:57 AM
#2
Usually, the ballast has gone bad when this happens, but when the lights work momentarily, that kind of shoots down that theory. My best guess is that the ballast is weak and overheats into failure mode. Change the ballast and see.
03-28-2022, 11:58 AM
#3
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read HID driver module...
You had the dealer replace the headlight control unit and tried to swap the HID bulb...
Now you need to read the faults in control module to help understand why it's predictably turning off. Ballast is a prime candidate but your hands-on testing indicates otherwise.
The old days are gone, you need a good scanner to diagnose headlight systems. Xentry-Star will do, aftermarket China scanners: unsure of coverage.
Now you need to read the faults in control module to help understand why it's predictably turning off. Ballast is a prime candidate but your hands-on testing indicates otherwise.
The old days are gone, you need a good scanner to diagnose headlight systems. Xentry-Star will do, aftermarket China scanners: unsure of coverage.
