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Exterior but no interior lights?

Discussion in 'A3/S3/Sportback (8P Chassis)' started by Vertigo1, Mar 4, 2007.

  1. Vertigo1
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    Vertigo1 Well-Known Member

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    [Mar 4, 2007]
    Weird one today with the light and rain sensors. My previous A3 had only the light sensors and I'd often find that it wouldn't switch the lights on in heavy rain as there was still enough ambient light to prevent it. No problem, I just had to switch them on manually in such situations.

    With the rain sensor on the new one, the car not only uses this to trigger the wipers but it also contributes towards the triggering of the lights, so when it's raining the lights will be switched on at a higher ambient light level than if it were dry. Apparently this is no uncommon for cars with both light and rain sensors and obviously makes sense.

    Today however, I had something really weird. Driving along the M6 in torrential rain but adequate light, I noticed that the exterior lights were on but none of the interior ones were! No dashboard or instrument illumination and the interior light pack LEDs weren't on either. What I'm wondering is whether this was the system being clever and realising that the exterior lights were only being triggered due to the amount of rain rather than lack of light and so the interior illumination wasn't needed? Or, more likely IMO, the computer just had a brain-fart and "forgot" to turn the interior lights on :)
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  3. newbiecrg
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    newbiecrg windsurfer

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    [Mar 4, 2007]
    Do you have daytime running lights? Could you it be them only?

    Anyway, if not, it is weird...

    Pedro
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  4. JamS3
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    JamS3 Active Member

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    [Mar 4, 2007]
    The ambient level of light is low so your outside lights have come on - this level is taken from the sensor in the rear view mirror next to the on button.

    The dash instrument lighting level is taken from a sensor at the bottom right corner of your speedo, it just won't have been dark enough to trigger the dash lights.

    This happens sometime with mine and my sat nav, outside lights on which you would expect the nav to go into night mode as they have gone on, but no it stays in day mode as the reading from the dash sensor gets enough light.

    Clever cars!
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  5. Vertigo1
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    Vertigo1 Well-Known Member

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    [Mar 4, 2007]
    Err, no. That sensor is purely for the auto-dimming rear view mirror (and wing mirrors too if you have those)
    Has it been raining when this happens? I'm convinced it's a facet of the rain sensor contributing to the decision to put the outside lights on yet not bother with the inside ones.
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  6. JamS3
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    JamS3 Active Member

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    [Mar 4, 2007]
    Erm its not trust me!

    Your lights don't come on just because of the rain. There IS a sensor that works them from the auto dim rear view mirror.

    Iv'e done loads of testing with the sat nav, the two sensors work together. Your outside lights will come on if the ambient light level is low but if the clock pod sensor is getting enough light the instument lights wont come on until its dark/darker.

    You will be able to see the sensor in the lower right of the speedo, shine a torch at it when its dark and even if you turn the clock brightness to minimum they will brighten up if a torch light is shined in the sensor! Vice versa if it is dull the clock instruments wont be as bright. This is very noticable with my sat nav to a point of lowering the drivers window you can see the screen brighten with the extra light the sensor gets. Bit annoying as you can't set the brightness and leave it as you want now as the car decides as to the light level.

    There is some info on www.navplus.us re this.

    Wait for a dull morning and you will see!
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  7. JamS3
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    JamS3 Active Member

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    [Mar 4, 2007]
    Just noticed you have dvd sat nav, go out and shine a torch beam into the sensor and watch your map screen light up!
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  8. JamS3
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    JamS3 Active Member

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    [Mar 4, 2007]
    Taken from Audi Site: 3rd Paragraphs covers rear view mirror and headlights

    The rain sensor activates the windscreen wipers automatically if it starts to rain or if there is any other moisture on the windscreen and adapts the wiper interval to match the amount of rain. How it works: light-emitting diodes inside the rain sensor emit an invisible infrared light which is reflected by the outside surface of the windscreen and measured by photodiodes. If the full amount of light returns to the photodiode then the windscreen is dry. A film of water or drops on the windscreen break up the light emitted. As the measuring process is permanent, the electronics can control the wiper intervals perfectly.

    The light sensor measures the surrounding light conditions with the aid of a photo cell and switches on the low-beam headlights automatically at dusk. The light sensor comprises the coming home / leaving home function. When leaving the vehicle, the front fog lights, tail lights and number-plate light are switched off after a certain delay (coming home) and switched on when the driver unlocks the doors with the radio-operated remote control or the advanced key (leaving home). The car?s outside lights can thus be used to light the way to the front door or the vehicle in the dark. On the new Audi A6, the time delay before the lights are switched off can be adjusted via the MMI system - for example, to coincide with the amount of time it takes to walk from the vehicle to the house.

    The automatic-dip inside and outside mirrors identify excessively bright headlight beams behind the car and darken the mirror glass automatically. An electronic control unit varies the darkening effect quickly and continuously according to actual ambient light conditions.
    The automatic dip function makes use of a transparent, electrically conductive material that becomes increasingly impervious to light when an electric current is applied to it. A very thin layer of this material is inserted between the actual mirror reflector and the outer glass.
    The mirror also contains two photo-electric cells. One of these faces forward and determines the ambient light intensity, which it converts into an electrical signal. The second is in the rear-facing surface of the mirror, and reacts when a bright light strikes it from behind the car. If this light is very much brighter than the ambient light intensity, the photo-electric cell generates the necessary electrical signal immediately, the electrically conductive layer darkens and the image in the mirror no longer dazzles the driver.
    In some models, the automatic-dip inside mirror is available with a light sensor, which switches the dipped-beam headlights on or off according to the ambient light level.
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  9. Vertigo1
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    Vertigo1 Well-Known Member

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    [Mar 4, 2007]
    There are a variety of sensors scattered about the car, including one in the back (i.e. the opposite side to the glass) of the rear view mirror, one (or maybe more) in the "bracket" into which the mirror connects and apparently one on the dashboard in one of those raised black things beside the vent/speaker in the middle.

    Firstly, I can well believe that any or all of these are used to measure the ambient light levels. I understand what you're saying about the exterior and interior lights being illuminated separately but this is the first time I've noticed it happening and it happened to be chucking it down with rain at the time. Perhaps it's a combination of the light sensors and the rain sensor thus making the separate illumination more likely when it's raining. This would, after all, make sense as you want the outside lights on in heavy rain but there's still loads of ambient light so don't need the interior illumination.

    The only thing I'd dispute is your comment about the light sensor in the front (i.e. glass side) of the rear view mirror, next to the switch. This is purely for measuring the light coming from behind the vehicle for the purpose of adjusting the mirror dimming and thus won't contribute to the switching of interior or exterior lights as neither of these has any bearing on how much light is coming from behind the car.
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  10. JamS3
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    JamS3 Active Member

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    [Mar 4, 2007]
    Well the last sentence in my post above explains it!

    The rain sensor has nothing to do with measuring light or turning lights on. The rain sensor activates the windscreen wipers automatically if it starts to rain or if there is any other moisture on the windscreen and adapts the wiper interval to match the amount of rain.

    How it works: light-emitting diodes inside the rain sensor emit an invisible infrared light which is reflected by the outside surface of the windscreen and measured by photodiodes. If the full amount of light returns to the photodiode then the windscreen is dry. A film of water or drops on the windscreen break up the light emitted. As the measuring process is permanent, the electronics can control the wiper intervals perfectly.

    Its just one of those things you have only noticed now, I spot things all the time and most of the time I think something is wrong but its just new technonogy I don't know the car has!
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