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Discussion Starter · #1 ·
Anyone else notice that certain HID-equipped cars following you can cause your autodimming rearview mirror to stop autodimming?

The other day, some sort of Acura was behind me, rather white HID's. They weren't on high or anything, but whenever he was directly behind, even fairly far back, my mirror went to daylight mode (no green tint). If a car came between, the mirror rapidly went green and dimmed normally.

At one point, a group of three or four cars with conventional lamps came up on us, and caused the mirror to respond just slightly. It wasn't until he moved to the right lane (at that point I was in the center) that the mirror really dimmed. And, when he moved back to center, it went back to clear.

I know that these mirrors have two sensors, a daylight sensor and a headlight sensor. The daylight sensor tells it whether it's dark, which enables the dimming. Then, the headlight sensor tells it to actually dim.

I thought the daylight sensor was in the back (facing the windshield), and the headlight sensors in the front (the teardrops below the glass). I guess the headlight sensors are involved in daylight sensing though, because even at night when not dimmed, the glass goes a little green. With the HIDs on me, this mirror went all-clear.

I have never noticed this before, and frequently have had HID cars behind me of course. Anyone else seen this, and/or know what might be different about an Acura's HID?

Tom.
 

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Re: Autodimming rearview mirror and HID car behind (tmtalpey)

Just a thought and a possible suggestion to others: the accuracy and speed of my auto-dimming mirror was greatly enhanced after I moved my [Mass. Turnpike] toll pass transponder to the left side of my mirror. I thought that the forward-facing light sensor had a clear shot around/beside the transponder - but I found that this was not the case.

The transponder instructions recomend that it be placed on the right side of the mirror - but it works fine on the left side.

John
 

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Re: Autodimming rearview mirror and HID car behind (tmtalpey)

I think the headlight sensor is on the front of the mirror. When my wife sits in the back, middle seat next to my son, her head will block the headlights from hitting the rearview mirror, and my mirror remains in daylight mode
 

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Discussion Starter · #4 ·
Re: Autodimming rearview mirror and HID car behind (bpwrightwv)

Definitely on the front of the mirror, as I said the two lenses below the glass. If you cover them both up at night with cars behind you, the mirror will brighten.

John - yes, the mirror's daylight sensor needs a clear view out the windshield. I don't have a transponder or anything else on mine. But the mirror sensor is on the driver's side. When you say "left", you mean driver's or passenger's? Because of the angle, the sensor would be very close to a transponder, if it were on the Driver's...

Tom.
 

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Re: Autodimming rearview mirror and HID car behind (tmtalpey)

Quote, originally posted by tmtalpey »
Definitely on the front of the mirror, as I said the two lenses below the glass. If you cover them both up at night with cars behind you, the mirror will brighten.

John - yes, the mirror's daylight sensor needs a clear view out the windshield. I don't have a transponder or anything else on mine. But the mirror sensor is on the driver's side. When you say "left", you mean driver's or passenger's? Because of the angle, the sensor would be very close to a transponder, if it were on the Driver's...

Tom.

I am getting confused with the terminology in this thread...

If we call the mirrored surface the 'FRONT' of the mirror and the surface that faces the windscreen the 'REAR' of the mirror, there is a sensor on each side.

The REAR sensor is the daylight sensor which points out of the windscreen and looks like the sensor in the bottom right of the Autodimming mirror in this photo:



The FRONT sensor points out of the rear of the car is senses headlights dazzling from behind you.

There are two things that come to mind as possibilities:

1. The frequency of light produced by certain cars is perhaps out of the spectrum that the sensor can handle.
2. Some of the light dazzling from behind is reflecting back from the inside of the windscreen and hence confusing the daylight sensor (again, could be frequency related.

Regards
UKMatt
 

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Re: Autodimming rearview mirror and HID car behind (bpwrightwv)

Quote, originally posted by bpwrightwv »
I think the headlight sensor is on the front of the mirror. When my wife sits in the back, middle seat next to my son, her head will block the headlights from hitting the rearview mirror, and my mirror remains in daylight mode

That would be her blocking the rear facing dazzling headlight sensor, not the daylight sensor (and of course, without any evidence of headlights dazzling you, it would remain in 'daylight mode').

UKMatt
 

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Re: Autodimming rearview mirror and HID car behind (ukmatt)

Quote, originally posted by ukmatt »
That would be her blocking the rear facing dazzling headlight sensor,

UKMatt

that's what I meant, which, to me, is on the front of the mirror-the mirrored surface
 

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Discussion Starter · #9 ·
Re: Autodimming rearview mirror and HID car behind (Parts @ Boston Volvo)

Quote, originally posted by Parts @ Boston Volvo »
By "left" I meant the drivers side. The daylight sensor on my daily driver is on the right front of the mirror.
Your DD is an S40/V50? Mine's on the driver's side.

Oh - I have the compass version (versatility pkg). Maybe the non-compass one has it different?

Tom.
 

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Discussion Starter · #10 ·
Re: Autodimming rearview mirror and HID car behind (ukmatt)

Quote, originally posted by ukmatt »
That would be her blocking the rear facing dazzling headlight sensor, not the daylight sensor (and of course, without any evidence of headlights dazzling you, it would remain in 'daylight mode').
In my experience, the mirror is pretty much clear in daylight mode, but goes green and dims slightly in twilight. Then, when headlights appear behind you, it dims further.

My HID-behind experience is that it goes completely clear, as if the sun was up.

Tom.
 

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Re: Autodimming rearview mirror and HID car behind (Parts @ Boston Volvo)

Same deal here, have the compass and autodim. I rarely see it dimming at all. Cars normally have to be within 3-5 lengths before it turns green, sometimes not even then. Never consididered it could be HIDs in the rear view. Usually have to adjust the aiming point to get it to turn green, could be a narrow field of sensing?

Also have the compass and IMO it would have been better positioned on either the plastic (make it a little bigger) or to the left of the mirrored glass. We need all the mirror we can get with the blind spots on our babies.
 
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