Strange auto lights behaviour

[AngryYeti]

Hi all,

I noticed on my way home the other evening that my headlights had come on (switch in auto position) even though it was a nice sunny day. I got home and cleaned the screen, where the sensor is, turned the lights off and then back to auto but they came on again. I thought it must be a duff sensor. Then I used the car later in the day and the headlights stayed off (still with the switch in auto). I thought the car must have got 'confused' earlier in the day.

This morning I start the car with the lights in auto and the headlights come on. Again, it is a bright sunny day. About 45 mins later, with no change in conditions, they turned off automatically. Now I'm thoroughly confused. Before phoning the dealer and getting it looked at I thought I'd see if anyone else had had this issue?

[ernieb]

I have found that the new car is more sensitive than the old.  So is does come on more when we might think it's light enough.  Have you checked what auto light functions are being controlled in the Maxdot?  Leaving home, tunnel etc.

[AngryYeti]

I thought it was just overly sensitive but it isn't flicking on and off enough to indicate it is on the edge of switching on/off, if that makes sense. It seems to either be on or off but not necessarily at the right time (maybe I have the Eric Morcambe option lights).

The light assistant settings (leaving/coming home) are both set to on. They tally with what I'm seeing when I start the car. I.e. When I blip the key fob the lights come on and when I start the car the lights come on.

[ejstubbs]

I've seen the auto headlights on my Yeti behave in a similar fashion.  I believe that the low sun at this time of year can 'confuse' the sensor for the auto lights, especially if it is bright sunshine.  The fact that you noticed the behaviour in the evening and in the morning (as have I) would tend to support that hypothesis.

 

I say 'confuse' but it's equally possible that there's a good reason for it, given the limitations of relying on a single sensor to trigger the appropriate action in a very wide range of different light conditions.  Put it this way: I don't think it really matters if the headlights occasionally decide to turn themselves on when it's sunny - I'd be much more worried if they didn't come on when it's dark!

 

I thought it was just overly sensitive but it isn't flicking on and off enough to indicate it is on the edge of switching on/off, if that makes sense. It seems to either be on or off but not necessarily at the right time (maybe I have the Eric Morcambe option lights).

 

I believe the auto lights have some kind of hysteresis built in to their logic so that once they're on, they stay on for a while and don't 'hunt' between on and off.  I suspect that being rapidly and repeatedly switched on and off would not be healthy for the xenon bulbs.  (OTOH I have a feeling that I read somewhere that the headlights on the facelight Yeti use a halogen bulb for dipped beam, so maybe that's a red herring.)

Edited 6 October, 2016 by ejstubbs

[keeff69]

Even though it's a sunny start to an Autumn day, the actual light levels will probably be very very low in real terms, and so low enough to trigger the lights.

 

In a previous existence I needed to measure light levels in glasshouses and what seems bright to human eyes often isn't.

 

Keith

Edited 6 October, 2016 by keeff69

[AngryYeti]

Put it this way: I don't think it really matters if the headlights occasionally decide to turn themselves on when it's sunny - I'd be much more worried if they didn't come on when it's dark!

That's a very good point!

The low sun would be a possible explanation. It would be nice to be able to turn the sensitivity down in the settings menu somewhere.

[ernieb]

As ejstubbs says, hysteresis.  Once 'on' the 'off' light level has to a bit higher than the original 'on' level.

[Llanigraham]

That's a very good point!

The low sun would be a possible explanation. It would be nice to be able to turn the sensitivity down in the settings menu somewhere.

 

Or how about just using the On and Off switch and ignoring the Auto setting? 

[Alexul]

I also believe that in uncertain conditions the lights are programmed to stay on, just to be on the safe side. What are those conditions it depends for each car manufacturer I guess. When I go into tunnels all the cars turn on their light almost at the same time. When exiting the tunnel, it is not rare to still have my lights on when the car behind me "decided" to turn them off. Especially if the sun is behind the car it will take a lot of time until the Yeti turns them off. Another situation I experienced was while driving in the Alps, in the valleys, tall mountains on both sides of the road, sun and clear sky but my lights were on because of the shadow areas.

[freedie]

If the sun is behind the car, and the car has an auto-dimming rear view mirror, then the lights "know" to stay on. Standard auto lighting feature. So you could turn off the auto-dimming feature on your rear view mirror if you object to the lights remaining on with low sun behind you...

Edited 6 October, 2016 by freedie

[don_kiddik]

If the sun is behind the car, and the car has an auto-dimming rear view mirror, then the lights "know" to stay on. Standard auto lighting feature. So you could turn off the auto-dimming feature on your rear view mirror if you object to the lights remaining on with low sun behind you...

Is the sensor behind the mirror glass?, I can see a sensor of some sort on the windscreen side of the mirror, or is it for something else?

[PaveyArk]

Is the sensor behind the mirror glass?, I can see a sensor of some sort on the windscreen side of the mirror, or is it for something else?

The one behind the mirror glass is for the auto dimming mirror and drivers mirror. Cover it with a finger and the mirrors go dark.

As for the auto lights, you can tell when they come on and off during the day as the SatNav on my L&K alternates between daylight and night time displays.

[don_kiddik]

The one behind the mirror glass is for the auto dimming mirror and drivers mirror. Cover it with a finger and the mirrors go dark.

As for the auto lights, you can tell when they come on and off during the day as the SatNav on my L&K alternates between daylight and night time displays.

On my Yeti there are two small leds by the interior lamp that light up when the lights come on

[ernieb]

They stopped putting the LED lights on the mirror when they changed it for the crazy small thing that's now fitted.

[137699]

This is not a Yeti thing but an Auto Lights thing. I have owned 4 cars (all different brands) with autolights and they all do similar in strong low sunlight.

 

A friend who works for ford tells me that they're designed to come on in such conditions because when you're driving into dazzling sunlight your pupils are already mostly closed to compensate, so when you look in the mirror you need the car behind to be as bright as possible in order to see it more easily.

 

Whether this is true or not I'm not sure, but it does make some sense.

Edited 7 October, 2016 by 137699

[TruckbusUK]

They stopped putting the LED lights on the mirror when they changed it for the crazy small thing that's now fitted.

 

Ah, I thought it was something to do with the sun roof .... the plastic moulding has the openings for small "mood" led's but nothing lights ... as I said I was under the impression it was something to do with the sunroof, sure I read it on these forums somewhere.

[CFB]

They stopped putting the LED lights on the mirror when they changed it for the crazy small thing that's now fitted.

Ernie, mine has the smaller mirror fitted.

It still has the 2 LED lights in the roof console.

As for the auto lights, I believe that low sun behind keeps the lights on to make the car more visible to oncoming traffic.

I have discovered that if you drive at 80mph plus (indicated speed) for more than a couple of minutes, the lights also come on.

They do the same when the auto wipers start sweeping continuously.

A sophisticated bit of kit that I'm happy to let do its thing.

[Ryeman]

All these features are for the safety of the driver, but what happens when there is no longer a driver I wonder?.

[Falmouthboy]

Or how about just using the On and Off switch and ignoring the Auto setting? 

I'm not 100% certain, but in 'on' rather than 'auto' I don't think the lights do their 'adaptive' thing whereby they focus at different ranges depending on your speed and if the wipers are on. They still do the 'bendy bendy' thing when you go around a corner though.

[Falmouthboy]

Ah, I thought it was something to do with the sun roof .... the plastic moulding has the openings for small "mood" led's but nothing lights ... as I said I was under the impression it was something to do with the sunroof, sure I read it on these forums somewhere.

Correct - if you have a sunroof you don't get the mood lights as the roof control swithc position would cause the relocation of the mood lights to reflect in the rear view mirror. Also, I'm not sure that you get them in S spec cars, only SE and above.

Edited 8 October, 2016 by Falmouthboy

[weasley]

The human eye and brain are very good at compensating for low light, so what looks like bright light to you can actually be low light levels, enhanced by your eye and brain. The sensor can only work with the photons available, which may be fewer than you think.

Similarly in daytime fog - it looks a bit grey and dim to you but there is a lot of diffuse light about so the auto lights often stay off... cue countless Audis, Mercs, BMWs et al flying down the outside lane in fog-coloured cars with no lights on.

[Ryeman]

Sadly it seems to be more macho to not think about your visibility

[Llanigraham]

They stopped putting the LED lights on the mirror when they changed it for the crazy small thing that's now fitted.

 

I don't think they have ever fitted LED lights actually on/in the mirror.

 

I'm not 100% certain, but in 'on' rather than 'auto' I don't think the lights do their 'adaptive' thing whereby they focus at different ranges depending on your speed and if the wipers are on. They still do the 'bendy bendy' thing when you go around a corner though.

 

I rarely use "auto" and my lights are still doing all the same things.

[aerofurb]

If you search the Yeti forum for 'cat's eyes' you'll find the subject of the overhead LED lights covered since the dawen of the Yeti.

 

It is a combination of overhead panel (sunroof, alarm type etc) and the installation of the mirror assembly that encompasses the light/rain sensor. On TIBETs I-III - all have had sunroofs and 'sensor' mirrors and if the cat's eyes were working they would merely shine onto the top of the mirror.

 

The Columbus in TIBET I did do its day/night thing, linked to the headlight light sensor. TIBETs II & III have had the Columbus do its own thing (ie lights switched 'off') but the satnav display changed as the ambient light level changed. I just leave it in 'night' mode which works just fine. 

 

Auto lights are fine - but they only measure ambient light levels and do not monitor visibility which is, in my humble opinion, just as important as ambient light levels. Until the sensors monitor visibility, I'll switch the lights on manually (to the 'auto' setting to get full use of the headlight functions).

 

The only issue I have is the ridiculous 'lights on' indication which makes no sense, having to look at the switch and suss what the switch lights mean - pre FL TIBETs I & II had a 'lights on' indication in the instrument cluster. 

 

 

 

PS There is an LED light actually on the mirror lower edge to show that the auto dipping mirror is switched on.

PPS The headlights (certainly the Bi-xenon ones) don't do their driving condition range changing and other stuff if switched to 'on' rather than 'auto'. It's in the manual....!

Edited 8 October, 2016 by aerofurb

[ernieb]

I don't think they have ever fitted LED lights actually on/in the mirror.

I think I've probably confused the issue, I meant not lights as such but the two small, single LED, lights that were part of the old bigger mirror. I'd prefer that mirror to the one I currently have, it's a weird shape and a restricted view for me.