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Discussion Starter #1
I know this has been posted a fair bit lately, but I jsut can't seem to get my head around it.

I have an 04 ARC, factory Xenon lights with the auto level. I've done the manual 666 high beam mod if that has any bearing on it, I don't think it should.

About 2 years ago my auto level warning came on, at the exact same time my passenger xenon bulb started flicker and turning pink. I picked up a pair of replacement cheapie bulbs and as soon as I installed them the warning indicator turned off. About 10 months later the same thing happened, but the bulb had not yet started giving me trouble...though it did start turning pink a month or so later. Bought another set of bulbs, but the indicator light is still lit and my bulbs are pointed full down.

At startup the bulbs cycle what looks to be their full up/down range, settle on the middle and then a very short time later the warning light comes on and the bulbs move to their full downward position.

I've bounced the front and up and down and I can hear the level motors cycling.

I've lifted the rear end with a jack and the lights move back to their middle setting and the indicator goes off when I'm a couple inches high. Tried doing a jerry rig fix with a set of coil spring helpers, but I don't think I can stretch the springs enough to get it. Warning light is still on.

One additional bit of info, I hit a raccoon awhile back, messed up my bumper cover (passenger side fog light mounts broken, grillwork on that side cracked and broken up some, plastic clips that hold the bumper cover under the front of the hood all broken off, tore off half of my lower splitter) and while it didn't smash anything to smithereens I'm not sure if it might have impacted the right light housing enough to maybe bend the mounts slightly...I'm not sure if that could have an effect on the leveling or not.

So I think my level sensors are working if the lights move up and down, but I'm unable to get it back in sync. Anything to be gained by disassembing the front end to see if there's any hidden damage around the headlamp mount? Its all solid, but it could be slightly out of true. Am I stuck and need someone with a Tech II at this point to see if the car will tell me whats wrong? If so, does anyone have a Tech II in either the Albany, NY area (work) or Kingston, NY area (home)?

Thanks.
 

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'02 9-5 Aero Wagon, '88 SPG, '02 Viggen Vert, '01 Viggen 4dr, +Triumphs & MGs
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Have you reviewed the front and rear level sensors to see any obvious damage? I would check the sensors and the arms first, as they are both on the right side and hitting a raccoon could have done something. I think it is less likely that your lights themselves have an issue. Especially as if you jack the car up it seems to change things...that says to me a sensor may be likely first culprit.
 

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Discussion Starter #3
I've inspected both sensors and there's no physical damage. Pulled both plugs and cleaned them as best I could and re-seated the connectors. Nothing obvious to me.
 

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My fiance's '02 9-5 Aero has the same apparent problem. Brand new leveling sensors. the headlight motors cycle up and then settle down. But the headlight leveling dummy light is always on.
 

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Have you double checked wiring looms and connectors for corrosion.
About half of sensor issues caused corrosion on wirings and/or connectors.

Are both lights at same brightness and same color?
When some erratic is present, lights are down for "safety".
 

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Discussion Starter #6
I've checked the wiring at the sensors, but not elsewhere.

Both lights are the same color and intensity. They look great, just pointing down.
 

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Don't have one or know anyone with one.

In my first post I asked if anyone local to me has one, otherwise I'll have to find a shop with one.
 

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A Tech II would prevent all kinds of guessing.

However, your symptoms sound like the rear sensor is not working correctly. I have had this issue with a (front) sensor from Saab, where it does not put out reasonable readings in the operating range. (With a Tech II, you can see what the front and rear sensors are reporting.)

What you can try is disconnect the rear sensor physically from the control arm, and move the sensor arm by hand. If moving it up or down a ways immediately makes the warning light go out and the headlights move to the proper position, that's a start. If you can move it into a range where the warning light is off, try moving the sensor up and down a little bit, and if the headlights do try to level, then it's got to be the sensor. It's just not working properly in the important part of its range.

Unfortunately the back sensor is the critical sensor for the system. You could leave the sensor arm detached and zip-tied so that the warning light is out. Then manually adjust the headlights to suit. The front sensor will still work the headlights (e.g. compensating for the front end dipping under braking) but the more important load levelling will be disabled.
 

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Discussion Starter #10
This is actually a brilliant solution, thank you. Can't believe I didn't think of it myself. My car is typically just a commuter and I rarely carry much in the way of passengers or much weight in the trunk, so the inconvenience of not having my lights adjust down a bit is minimal.

Thanks.
 

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This is actually a brilliant solution, thank you. Can't believe I didn't think of it myself. My car is typically just a commuter and I rarely carry much in the way of passengers or much weight in the trunk, so the inconvenience of not having my lights adjust down a bit is minimal.
One thing to keep in mind is that the headlights might level to some fairly far-out extreme (upwards, I'm thinking) when you set the level sensor to a "good" part of its range. We don't know what suspension deflection the sensor may report in its working range. It may also vary randomly on its own, or under very minor vibrations. (Again, no way of telling without a Tech II hooked up to see what it reports when it is working.)

You should be able to manually adjust the lights to a reasonable level, but ideally, they should be calibrated via Tech II which makes the current level sensor reading the "default" position and puts the lights roughly midrange. Then you manually adjust to be just right.

To unpack "calibration". The sensors report a position in percent, where around 40% (as I recall from WIS) is the expected position reported in a fully-fueled but unloaded car. The percentage changes as the suspension height increases or decreases (and it's an opposite change front or rear). The headlight also has something like 250 steps of height adjustment. The "normal" position is something I forget, but it's in the WIS. Anyway, calibration tells the headlight module "remember the current front and rear level sensor readings; when they read that, the car is level and therefore set the headlights to level" (level being the normal positon).

Obviously if the rear sensor will be permanently reading 15% or 88% or whatever, then the headlights will adjust to some height setting that's way different from "normal", because the system is being told that the suspension height is way different from normal. Tech II calibration will resent that 15% or 88% as normal. Well, I expect it will; I don't think the modules will say that "hey, 88% isn't normal!"
 

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Don't have one or know anyone with one.

In my first post I asked if anyone local to me has one, otherwise I'll have to find a shop with one.
I live in Guilderland, NY and have one.
 

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Sure you can PM me for my details if you would like.
 

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In case anyone wonders if the two sensors are really different. They Are. My rear sensor has "4MHz Angle 0" printed on it, while the front has "4MHz Angle 90".
Testing with the Tech 2 showed that the front sensors has a correctly working range +- 45 degrees with the arm 90 degrees to the connector pin direction. It will not work in the rear position as the orientation of that sensor uses an arm position +-45 degrees with the arm in line directly away from the connector pins.
As quoted elsewhere concerning the corrosion: there is an extra connector set in the cable line with the front sensor. I have not found mine yet.
My Tech2 symptoms implicate both front and rear sensors but I have found that the rear seems to be dead. I must check with the front replaced where it came from.
The sensors have a keying signal which might tell the units if they are masters or slaves. The Master would produce a pulse/signal and the slave would wait until it sees the master and then produce its own set of pulses. I have not looked at the signals yet..
 

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I am not so sure if the actual guts of the sensors are different. However, they are supplied reverse polarities, so one puts out a signal that must drop from +5V, while the other puts out a signal that rises from 0V.

WIS states that both units send a 200Hz PWM signal. Somehow the headlight modules can decipher the signals, since both get combined on one wire that goes to both modules.

While I agree that the front sensor won't work if installed in the rear, and vice-versa, I suspect that if you plugged the front in the back, or vice-versa, and rotated the shaft enough, you would get sensible level signals.

No guarantee if you blow your car up trying this, though. :roll:

(Ideally, if I was bothered, I'd pull out the old Heathkit oscilloscope and see what's actually going on.)
 

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Funny you should say that.. I tried the front sensor in the rear position. It produces a signal that the car understands but the angle is 90 degrees off. With almost no load it reports 89 percent (Tech2 numbers). The headlights get pointed skywards... Removing the bracket on the arm so that I could move the arm revealed that a linear response was produced wth the arm in the 90 degree position. Hence my report over. Pin2 is connected high on the front and low on the rear. I suppose that the boxes are the same, but the arms are fixed at the required angle. Pin 2 tells the electronics if it is master or slave.. I will post curves if I manage to probe the connector.
 

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Pin 2 tells the electronics if it is master or slave.. I will post curves if I manage to probe the connector.

There is, as far as I understand it, no "master" or "slave". Front and back send the same kind of signals, but opposite polarity.


The system does treat the rear sensor as more important. If only the front sensor has failed, you get the warning light on the dash but the headlights still autolevel based on the signal from the back. If the back sensor has failed, the headlights drop to the "safe" position, whether or not the front sensor is working.
 
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