Bi-Xenon Headlight Question
Thread Starter
Burning Brakes
Joined: Jan 2010
Posts: 1,228
Likes: 95
From: Atlanta, GA
Bi-Xenon Headlight Question
I recently purchased a 2003 C4S and noticed that the driver's side headlight was noticeably lower in aim direction than the passenger headlight. First thing I did was go to the Owner's Manual (pg 100) and noted that when you turn the lights on that the "light beam first dips all the way down and then adapted to the vehicle load". Very similar to other cars I have had w/ HID headlights.
Then I went to the section on headlight adjustment (pg 236). It states nothing to the affect that one headlight should be aimed lower than the other
My car does NOT perform this "self check".
So...I took the car to the dealer, who performed a check out of the system. They state everything is OK and that one headlight should be lower in aim than the other b/c of oncoming traffic.
My questions to everyone Bi-Xenon's - Does your P Car perform the self check when you turn on the headlights and is there a noticeable difference headlight aim direction?
...or is it owner error?
Then I went to the section on headlight adjustment (pg 236). It states nothing to the affect that one headlight should be aimed lower than the other
My car does NOT perform this "self check".
So...I took the car to the dealer, who performed a check out of the system. They state everything is OK and that one headlight should be lower in aim than the other b/c of oncoming traffic.
My questions to everyone Bi-Xenon's - Does your P Car perform the self check when you turn on the headlights and is there a noticeable difference headlight aim direction?
...or is it owner error?
Rocky Mountain High
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Joined: Aug 2007
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Likes: 2,865
From: Kolorado
My driver's side headlight is lower, as expected and as your dealer says.
The headlight self check is different on the 996 than on some other cars. On my Cayenne, the self check takes place when the headlights are turned on. On the 996, it takes place when the ignition is turned on. Turn your headlights on before you start your car, and you'll see it go through the cycle when you do start the car.
The headlight self check is different on the 996 than on some other cars. On my Cayenne, the self check takes place when the headlights are turned on. On the 996, it takes place when the ignition is turned on. Turn your headlights on before you start your car, and you'll see it go through the cycle when you do start the car.
Instructor
Joined: May 2007
Posts: 205
Likes: 0
From: YUL
My headlight beams have always been unequal height since I got my car...just thought it was mis-aligned, so I learned something new (again).
However, my lights used to self-level but don't anymore since the load sensor broke underneath the car. I was checking my brakes and noticed a small arm dangling freely from the driver's-side suspension...any direct hit to it will break it since it's partly plastic. And I'm sure of this because I have daytime running lights & and soon as the ignition is turned the headlights turn on.
If that piece is broken you will not get self-levelling. Think it's this part?
No. 996.341.375.01 (99-)
Angle sensor actuator strut
And it attaches to this piece:
No. 996.631.121.00 (99-)
Angle sensor for litronic headlights (2)
The first part is about $25 on Pelican Parts, the sensor itself is $83.
However, my lights used to self-level but don't anymore since the load sensor broke underneath the car. I was checking my brakes and noticed a small arm dangling freely from the driver's-side suspension...any direct hit to it will break it since it's partly plastic. And I'm sure of this because I have daytime running lights & and soon as the ignition is turned the headlights turn on.
If that piece is broken you will not get self-levelling. Think it's this part?
No. 996.341.375.01 (99-)
Angle sensor actuator strut
And it attaches to this piece:
No. 996.631.121.00 (99-)
Angle sensor for litronic headlights (2)
The first part is about $25 on Pelican Parts, the sensor itself is $83.
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Thread Starter
Burning Brakes
Joined: Jan 2010
Posts: 1,228
Likes: 95
From: Atlanta, GA
My headlight beams have always been unequal height since I got my car...just thought it was mis-aligned, so I learned something new (again).
However, my lights used to self-level but don't anymore since the load sensor broke underneath the car. I was checking my brakes and noticed a small arm dangling freely from the driver's-side suspension...any direct hit to it will break it since it's partly plastic. And I'm sure of this because I have daytime running lights & and soon as the ignition is turned the headlights turn on.
If that piece is broken you will not get self-levelling. Think it's this part?
No. 996.341.375.01 (99-)
Angle sensor actuator strut
And it attaches to this piece:
No. 996.631.121.00 (99-)
Angle sensor for litronic headlights (2)
The first part is about $25 on Pelican Parts, the sensor itself is $83.
However, my lights used to self-level but don't anymore since the load sensor broke underneath the car. I was checking my brakes and noticed a small arm dangling freely from the driver's-side suspension...any direct hit to it will break it since it's partly plastic. And I'm sure of this because I have daytime running lights & and soon as the ignition is turned the headlights turn on.
If that piece is broken you will not get self-levelling. Think it's this part?
No. 996.341.375.01 (99-)
Angle sensor actuator strut
And it attaches to this piece:
No. 996.631.121.00 (99-)
Angle sensor for litronic headlights (2)
The first part is about $25 on Pelican Parts, the sensor itself is $83.
Thanks for the advice/recommendation!
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Nordschleife Master
Joined: May 2005
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And yes, my driver side is a little lower than the pax side as well just like your dealer (and my dealer) explained.
Instructor
Joined: May 2007
Posts: 205
Likes: 0
From: YUL
I simply didn't bother replacing the part(s), since I don't really care if the headlights self-level. Not a big deal 
If you're curious just take a look at your lower control arms to see if there's a small arm hanging free.
If you're curious just take a look at your lower control arms to see if there's a small arm hanging free.
Thread Starter
Burning Brakes
Joined: Jan 2010
Posts: 1,228
Likes: 95
From: Atlanta, GA
Interesting comments on the left side headlight being lower than the right. As I stated, the manual makes NO mention of this whatsoever (pg236). It even goes into precise detail on how to set them up (which I've never seen in any manual).
Seems to be the prevailing thought, though...
Seems to be the prevailing thought, though...
Still plays with cars.
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Member
Joined: Jul 2001
Posts: 15,077
Likes: 264
From: Montreal
All cars with properly aimed headlights in North America have the driver's side light aimed lower than the passenger side to avoid blinding on-coming drivers. I suspect in the UK it is the reverse. I vacation on a island where you drive on the left side. May of the cars are US left hand drive. At night oncoming US cars are a real nuisance because their headlights are aimed wrong for the local rules.
Drifting
Joined: Apr 2006
Posts: 2,208
Likes: 2
First, standing outside the car and reaching in throught he window you should see the headlights lower and raise when you turn them on. Second, your headlights may not actually be at different heights, you just perceive it as so due to the beam pattern. If you look at the beam pattern and cutoff line, the pattern is stronger and higher on the side away from oncoming traffic, in our case to the right. In fact, the cutof line from the driver's side headlight blends into the passenger headlight.
With all that said and done, you can readjust the headlights, but you have to remove each headlight to do so. The up/down adjuster is not reachable with the headlight inside the car. Removal directions are in your owners manual. Adjustment is very easy and only requires using a philips screwdriver. Over a couple of years after installing a ROW M030 suspension in my car, as the car continued to settle lower (1.25" drop front and .75" drop out); so did my headlights. I didn't realize how low until I had a service loaner and saw how much higher they are on the new car. I readjusted mine and can't believe the visibility difference. It takes a little patience as you need to adjust just one headlight at a time. As you turn it up, you will also need to readjust the left/right adjustment to center it.
With all that said and done, you can readjust the headlights, but you have to remove each headlight to do so. The up/down adjuster is not reachable with the headlight inside the car. Removal directions are in your owners manual. Adjustment is very easy and only requires using a philips screwdriver. Over a couple of years after installing a ROW M030 suspension in my car, as the car continued to settle lower (1.25" drop front and .75" drop out); so did my headlights. I didn't realize how low until I had a service loaner and saw how much higher they are on the new car. I readjusted mine and can't believe the visibility difference. It takes a little patience as you need to adjust just one headlight at a time. As you turn it up, you will also need to readjust the left/right adjustment to center it.
Weathergirl
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Joined: Oct 2002
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From: SE PA
...your headlights may not actually be at different heights, you just perceive it as so due to the beam pattern. If you look at the beam pattern and cutoff line, the pattern is stronger and higher on the side away from oncoming traffic, in our case to the right. In fact, the cutof line from the driver's side headlight blends into the passenger headlight.
I've never heard of actually aiming the whole headlight bucket lower, though, which also affects the high beam.
And if that's true, then what effect should adjusting the height manually have? How would the self-adjuster know where the beam itself was pointed?
In the shop manual, the headlight aiming instructions specify that for Litronics, you should manually set the headlights to the same level, then turn the ignition off and on to allow the self-adjuster to move them, then set the level again. There's no indication that you should set them to different levels.