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In the past 3 months I have been through a number of (French) tunnels of varying lengths.  Headlights were set on auto but I noticed that the headlights of cars behind came on far quicker.  Mine seemed to take longer to react and also to take some time to switch off after leaving the tunnel.  In some cases did not switch off at all even on sunny bright days.  I don't know what is 'normal'.   Does anyone have experience of repeated on/off situations and the reaction speeds?  

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My RC reacts very quickly when going under a bridge. What sensitivity setting do you have your auto lights on?

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There were a few instances of IS models having dodgy sensors for the auto lights. 

However, if you have got your sensitivity to low then I would class the behaviour as normal. 

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Thanks for the information.  Hadn't thought of looking in the manual or that this function would be customisable.  Have now gone up one notch (range is minus 2 to plus 2) as I assume up means more sensitive.  We'll see!  

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i would set it to +2  so you will be able to see how the light react at the other extreme

moving up 1 notch maybe too small to see the changes.

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Wonder if I can do this on my GS300? Just it seems to keen and this time of year they are on and off throughout the day so worried about the wear on the bulbs.


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Its a dilemma.  Want the lights to come on quickly at tunnel entrances but don't want the lights to be turning on/off on country roads shaded by trees.  Going to start with +1 and see how this works out.

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There are situations where I find light sensitivity adjustments useful or even necessary.   Examples include long series of tunnels where the

intervals are mostly longer than the default 30' and the +2 maximum sensitivity setting is preferable to keeping the headlights permanently on,

and long stretches of road or narrow city streets and alleys with alternating patches of sun and shade where the minimum -2 setting can be

best unless you choose to turn off the auto function altogether.  As regards entry into motorway tunnels at high speeds, given that the distance

you travel into the darkness will be proportionate to the latter, the activation of the auto function - and your perception of it - may be fractionally

delayed if the sensitivity is set to Regular.  However, as a rule of thumb I established with an IS300h and have confirmed with my present RC, a

+2 maximum sensitivity setting enables the headlights to come on perfectly simultaneously with entry into a tunnel at 100-110kmh without

any perceptible delay in respect of lower speeds.  With the settings on Regular or +1 or at speeds higher than this I find the activation to be 

noticeably less "prompt".

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TBH I've always changed Lexus light sensitivity to -2 on every model

My 3RX, 3IS and 4RX all worked exactly as they should i.e turn on when dark and turn off when light. Nothing more annoying to me than people driving around with headlights on when its barely dark at all.

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Yes, me too! I have set mine to the minimum as, IMO, it is far too sensitive otherwise. 

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On 17/10/2017 at 4:15 PM, rayaans said:

There were a few instances of IS models having dodgy sensors for the auto lights. 

However, if you have got your sensitivity to low then I would class the behaviour as normal. 

I think Mine  might be one of the dodgy  ones , lights slow to come on, but come on in daylight under trees .one incidence when driving on motorway on sunny day and the lights did not turn off. Would Lexus change the sensors under warranty? 

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Auto lights are the biggest pile of poo ever to leave the drawing board in my humble opinion and nothing will ever surpass the human brain, human eyes and common sense!

All that switching on and off unnecessarily shortens the life of the ballasts on HID lamps and shortens the life of the bulbs. Worst of all though, are those numpties who haven't got the common sense to switch them off as they park up while they drop someone off or whatever. I know that happens even with manually operated lights as well but when I pointed it out to someone recently and asked them to turn their headlights off because they were dazzling oncoming drivers, the answer was, "They're automatic, I don't know how to"  :wallbash:

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You might be interested to know that on the 4RX you cannot turn the headlights off! What is normally the "off" position has now become "Auto".

While what you say about lifetime is probably true for HID lights, the new LED ones are insensitive to on/off cycling.

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Having read Rayaan's post before going out this morning, I thought I would try the -2 setting, which, except for a few times when I forgot to

re-set to my habitual "Regular", I have never normally used.   Apart from the headlights coming on with a slight and arguably undesirable

delay in one or two patches of very dark shadow, I had no issues with it.   However, upon entering a motorway tunnel at about 120kmh, the

headlights did not come on until I was three or maybe four car-lengths in.   Again, this would not be much of a problem in areas where 

tunnels or long stretches of shadow are few and far between but,  generally speaking, a higher sensitivity setting remains my choice.

 

If I understand Malcolm's last post right and Lexus allows the  headlights in the new 4RX to be turned off not manually but only via the auto 

function, I am surprised that any regulatory authority would allow it.   But if so, and Lexus extends this to all future models, it would oblige

new generations of owners to pay much greater attention to light sensitivity settings than many and probably most of us do today.

 

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Many current Mercedes models do not have an Off position for lights. I don't see this as an issue for the regulatory authorities (clearly it's not or they wouldn't have got type approval) as lights left on are not a safety issue. Whereas lights not coming on could be, as witnessed by me this morning with the number of numpties driving in rain and mist, virtually invisible until the last minute!

My RC seems to switch the headlamps on very promptly, I pass under a fly-over nearly every day and no matter the ambient light level, the lamps flick on the instant I pass under and remain on for ~10sec after exiting. The fly-over is only dual carriageway wide. The sensitivity is factory level, never  felt the need to change it. 

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Until I try it for myself, I will find it difficult to get my head around the possible consequences, beneficial or otherwise, of not being able 

to turn off the headlights before the auto system allows me to - if, indeed, this is the result of there being no OFF switch.  Not that I am 

unwilling to accept than an electronic nanny can do some things better than I ever could.  Far from it.   But I sometimes worry that my 

ability to decide for myself in situations of perfect normality is being undermined.

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On ‎16‎/‎10‎/‎2017 at 10:03 PM, BigChange said:

In the past 3 months I have been through a number of (French) tunnels of varying lengths.  Headlights were set on auto but I noticed that the headlights of cars behind came on far quicker.  Mine seemed to take longer to react and also to take some time to switch off after leaving the tunnel.  In some cases did not switch off at all even on sunny bright days.  I don't know what is 'normal'.   Does anyone have experience of repeated on/off situations and the reaction speeds?  

I travel through France 3 to 4 times per year and I have noticed the same with our RX450h, and previously our RX400h. I think this is either because French tunnels are comparatively brightly lit, or because of the orange tint of the lights used in tunnels. I usually switch the lights on/off manually.

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