Everything you ever wanted to know about auto dimming rear view mirrors

RareGMFan

Addict
Jan 12, 2008
934
176
Naperville, IL
Seeing as to how I'm frequently asked about information on self-dimming mirrors, I thought it would be a good idea to start an informative thread outlining how the mirrors work, the different brands and kinds there are, the pros and cons to those different kinds, as well as basic removal and installation instructions. My goal is to make this as thorough as I can, but if you still have some questions I didn't go over, please feel free to ask. I'm not an expert by any means, but I've been fascinated by these mirrors ever since I discovered them 10+ years ago, so I have gathered a decent amount of information about them. Forgive the quality of the pictures. I will update this post when I get a better camera and more ideal lighting.


Quick History & Background

Auto-dimming mirrors are nothing new by any means. The electrochromic technology used to make today's mirrors has been around since the '40s, and has been in use in automotive mirrors since the '80s. The concept of an auto-dimming mirror was first introduced by the Zeeland, Michigan based electro-optical products manufacturer Gentex Corporation. They created the world's first electromechanical mirror in 1982, which found its way into higher end American luxury cars as an option in 1983. It used sensors to detect glare from behind. The sensors were connected to a small motor that would move the angle of the mirror to adjust accordingly. In other words, it basically acted as an automatic version of the flip tab on standard mirrors. These mirrors would be available through '91.

In the meantime, a father and son team of chemists convinced Gentex that they knew how to apply electrochromic technology (a gel that darkens when electrically charged/clears with no charge) to their mirrors. After investing a lot of money for R&D, they found a way to sandwich a thin layer of the gel between 2 pieces of glass, and have it react to an electrical charge initiated by sensors mounted on the front and rear of the mirror when they detected glare. The first electrochromic self-dimming mirror was introduced in '87, and was made available in the '88 Lincoln Continental, and 8 GM cars in '89. They became more commonplace in the early '90s.

It is at this point that Holland, Michigan based Donnelly Corporation, another major automotive mirror manufacturer, came into play. Gentex' auto-dimming mirrors were a huge success, gaining more and more car manufacturer contracts. Donnelly was trying desperately to take back some of the market share by producing mirrors with very similar technology. In may of '90, Gentex sued Donnelly over patent violations. Through a mess of suits and counter suits over the next few years, as well as out of court settlements, things finally cooled down between the companies. In the meantime, Gentex continued to expand upon what they started with their mirrors. In '93, they introduced the first self-dimming mirrors with a compass that showed the direction you were headed in a little digital display within the mirror itself. These mirrors would become available on '94 model year luxury cars. From '97 - '98, cars would start receiving self dimming outside mirrors, inside mirrors that displayed compass as well as outside temperature, and compass mirrors with LED map lights, which were ONLY available as an option on the Intrigue GLS in '98. The GLS also had this same mirror available in an OnStar equipped version.

Fast forwarding to today, Gentex has grown immensely, and is regarded as the leading company in auto-dimming mirrors with distribution in several countries, including Germany and Japan. They have expanded their contracts to almost all car manufacturers around the world, and self-dimming mirrors are no longer something reserved for higher end luxury cars. They can be found in all sorts of makes and models in many variations. The features have also increased dramatically, including versions with HomeLink, back-up camera and navigation. Meanwhile, Donnelly lost a lot of ground in the war for market share since 2000, and is virtually non-existent in the manufacturer's contract department.


Gentex vs. Donnelly Pros & Cons

Being the 2 major producers of auto-dimming mirrors, these two have been dueling each other for a couple decades now. Virtually every feature Gentex came out with, Donnelly would copy. However, the 2 companies took a very different approach as far as aesthetics. Donnellys had more of an "egg shape" to them, especially if they had temp and compass, because they put the display for those in the base of the mirror as opposed to in the mirrors themselves like Gentex does. The front of a Gentex mirror looks more like traditional mirrors, but with a bit of an extension at the middle of the bottom for the buttons. Personally, I prefer the way Gentex' look a lot more, but that's subjective. One plus for Donnelly mirrors is that they are much more commonly available with map lights. Since most of the vehicles that Gentex' originated in were luxury, or well equipped, they usually already had some kind of fancy overhead console or dome light, so they scarcely received map lights in the mirrors.


autodim1.jpg

Fully optioned Donnelly mirror.

However, this and all other advantages for Donnelly mirrors are a moot point because of one monumental problem they're prone to which renders them useless. Donnellys are notorious for breaking and leaking the liquid inside of them, often causing discoloration in the paint when the liquid eventually drips onto the center console. Why is not completely known. However, I mentioned the legal troubles between the 2 companies earlier, and that Donnelly had to change their methods of accomplishing the auto-dimming effect due to patent infringements. My theory is that whatever they did to change the process for auto-dimming, it was an inferior process with poor reliability/durability. On the other hand, I've never really heard of a Gentex mirror failing in any capacity (certainly not by leaking out the gel). It is for this reason that I usually suggest people switch to a Gentex when their Donnelly mirrors finally fail, which they inevitably will.

Mmkay, now for the good stuff you've been waiting for.


Removing and installing auto-dimming mirrors

Removing factory auto-dimming mirrors from the windshield

*DISCLAIMER: The process for removing mirrors with the newer mounting style can put your windshield at risk for cracking or breaking. I am not responsible for any damage. Attempt at your own risk!

This will actually be the hardest part of adding/replacing an auto-dimming mirror. Rather than using the traditional, easy-to-remove single torx screw to tighten the mirror onto the windshield button, newer auto-dimming mirrors have a tensioned spring with tabs in the brackets that, once the tabs clear the windshield button, locks it into place, making removal a serious pain by comparison. To get an idea of what you’re dealing with, here is a mirror off the car with the spring/tabs exposed (tabs circled in blue). It is this spring that has to be pushed in towards the mirror so that the tabs on the spring will clear the mounting button, allowing the bracket to slide up and over it.

Mirrors1-1.jpg
Mirrors2.jpg



You will basically have to insert a small slotted screwdriver into the slot opening at the bottom of the mirror bracket’s base, and gently tap at the screwdriver (preferably with a rubber mallet) till it pushes the tab back far enough to clear the button. The screwdriver is in far enough when it won’t fall back out with little force, but at the same time, not so snug that it takes a lot of force to get it unstuck. Take your time, and check to see if it’s at this point with every few taps. Driving the screwdriver in too far can cause the windshield to crack or break. Here’s an off the car visual to give you an idea of what you’re looking for.

Mirrors3.jpg
Mirrors4.jpg



At this point, the mirror bracket should slide out by gently lifting UP on the mirror while wiggling it back and forth.

Mirrors5.jpg


Again, I have to stress to be extremely careful with the removal of these mirrors. The process itself sounds straightforward and easy enough, but the springs are often stubborn, so you have to be very cautious not to exert enough force to break the windshield.

Tip: If you do not feel comfortable trying to remove the mirror yourself, skip to the wiring so that’s in place, and then take the vehicle to a glass or body shop to pop the mirror off. Most will remove rear view mirrors for $10 - $15, and many will even do it for free! Same with reattaching mirrors that have fallen off!



Replacing/swapping factory auto-dimming mirrors

If your vehicle already came with a Donnelly or Gentex, and you're looking to swap mirrors for more features, or because your Donnelly broke, then this will be a fairly easy process, as all the essential wiring will already be there. The first thing you will need to determine is if you have the older style 3-pin harness, or the newer style 7-pin harness, as illustrated below.

Mirrors6.jpg


If you have the newer 7-pin style with only 3 wires coming out of it, then this will be a direct plug and play. If it is a 7-pin, but there are more than 3 wires present (i.e. your current mirror has map lights), then you will simply pull out the extra wires from the harness, and either cut them off at a point where you can’t see them anymore, or if you’d prefer to keep them in tact, wrap up the tips to prevent any electrical problems, and tuck them away in the headliner. You can then just plug in your existing harness into the new mirror.

If you have the older 3-pin harness, this will still be an easy swap, just slightly more time consuming/involved. Without loosing the order the wires are aligned in, remove the pins from the old harness with a small flat screwdriver. Do the same for the wires coming out of the harness on the new/replacement mirror.

Mirrors7.jpg
Mirrors8.jpg

Mirrors9.jpg


Next, with the new harness facing in the direction it will be in when plugged into the mirror, and the wires from your vehicle aligned in the same order they were in when removed from the old harness, push the wires from your vehicle into the pinouts in the new harness from right to left. A pin-out is provided after the next section.

Mirrors10.jpg
Mirrors11.jpg


Mirrors12.jpg
Mirrors14.jpg




Installing auto-dimming mirrors in non-factory equipped vehicles

If your vehicle came from the factory with a standard mirror, don't worry. An auto-dimming mirror can be installed into ANY vehicle with a very small amount of electrical know-how. All it will require is one wire running to a +12v that powers on with the accessories, and one grounded wire. The self dimming and compass features are self contained and need only that one power wire to function. The 3rd wire automatically disables the self-dimming feature when the vehicle is put into reverse, but most people seldom wire it, as it is an unimportant feature and not worth the trouble. If you have a mirror that shows outside temp, you will need to get a temp sensor as well, and run a wire from the sensor to the mirror. Whether you have a 3-pin, or 7-pin harness, the following is the correct wiring for the majority of auto-dimming mirrors with or without compass when looking at the front of the mirror with the harness plugged in. Obviously ignore the 7th pin if your replacement mirror doesn’t have map lights.


MirrorDiagram1.jpg


And that’s all there is to it! If you have any questions I haven’t gone over, please feel free to ask. BTW, I have amassed a rather large collection of fancy mirrors of all types, and will be posting a thread for them in the classifieds section soon. I will provide a link here when I do. All my mirrors are tested prior to sale as well. As a general idea, an auto-dimming Gentex or Donnelly is $55 shipped within the continental US. A Gentex with a compass or Donnelly with map lights is $70 shipped.

*EDIT* Got a bunch of mirrors listed: http://www.thechicagogarage.com/forum/showthread.php?t=57956
 
Last edited:

hellraiser319

Hellraising since 1986
May 17, 2010
1,323
0
West Bend, WI
I'm still terrified of those mirrors with the OnStar FMV program, but so far, this lil guy seems to do the trick with popping those ones with the spring clips off. Stick it in the top hole, gently pry, and mirror comes off. We have been using this instead of anything that pops it off from the bottom because that seemed to break a lot of windshields...

F30454779.jpg
 

RareGMFan

Addict
Jan 12, 2008
934
176
Naperville, IL
I've been tempted to get the "proper" tool for removing these mirrors, but have been putting it off because I've read mixed reviews on the ease of removal even WITH the correct tool. However, I've never seen mention of this one where the mirror is removed from the TOP. I'm curious as to how that would work. Can't picture how it would go down far enough to relieve the tension of the spring, but I guess I'd need to see it in action to get a feel for how it works.

Where might I pick one up, and how much are they if you don't mind me asking? If it's cheap enough, I'm definitely willing to give it a try.
 
My wife is absolutely nuts about these mirrors. You just made my life easier, thank you!

No problem. :) Honestly, for how long these have been available, and how many people have added them to such a wide assortment of makes/models, I'm pretty surprised no one has done an extensive write-up on them yet. At least not that I've come across. It's always bits and pieces of info on various threads asking about them, or maybe a write up on how to install a specific mirror into a specific car. That's why I decided to make one. Took a while to put together, but I think it will be worth it in the long run. BTW, believe it or not, this is more of a rough draft than anything. Eventually, once I get a better camera, I will elaborate on this even more. Maybe even video.



I really don't know why more cars don't have these. My 96 suburban has one from the factory. I wonder why they aren't installed more often in new cars.

Actually, from what I've seen, they've become a lot more common the last few years. When these first started out, they were basically reserved for higher end cars, or at least more expensive ones. Since big SUVs cost more than most cars, many of them received the mirrors (unless you got a really stripped down model). Nowadays, I see them in a lot of the middle of the road cars, and even some of the entry level cars. Obviously they're not in EVERYthing, but they've become a lot more available than in the past.



Have any auto dim mirrors w/ onstar buttons on them? They don't need to have the lights or compass.

I know I don't have one in my apartment, but I *MIGHT* have one in my storage space, where I've got a ton more parts, including mirrors, that I need to go through. I will hopefully find some time by this weekend to grab a few boxes and go through them.
 
That is how they came. Auto-dim was a given, compass was the next "upgrade", and then temp was added. There is no such thing as one of these mirrors with only temp, and no comp. HOWEVER, the earliest edition of Gentex with comp AND temp actually used the same single display screen as the comp only mirrors, so you had to toggle back and forth between the comp and temp in order to see each. You could get one of those, and just always leave it to display temp. They look identical to these, except with the edition of a temp button:

Mirror7.jpg





And I do NOT have a problem, Rich!! *twitches nervously*
 
Thought I'd update this thread with some new findings. My disdain for Donnelly mirrors has grown. A couple weeks ago, I literally had 3 of them not functioning properly when I tested them. I had noticed on my first failed one that the power for the compass, map lights and auto-dim would flicker when the wires moved. I wasn't sure what was causing it at first. I thought maybe the wires to my power supply were not getting a good connection, or moving, etc. Then I wiggled around the harness that was plugged into the mirror, and noticed it consistently flicker with movement, so something was loose from inside. Terrific! It was not worth the 1.5 hour round trip drive to get credit for it at the yard, and I couldn't sell it not functioning, so I figured I had nothing to lose if I opened it up, which was my first time doing so with a Donnelly (they're not meant to be opened, unlike Gentex mirrors). After wrestling vigorously to get it apart, I found that the 7-pins going out to the harness were loose at the circuit board. So I ran out and bought a small spool of solder and some super glue (to put the mirror back together later). Resoldered all 7 pins, super glued the 2 mirror halves since there's no other way to put them back together again, and plugged her in. PRESTO! Everything worked, despite shaking the hell out of the wires and mirror. Great! :) One down.....two to go, as I would later find out. :rant: BTW, I sold that first mirror for $120 shipped a couple weeks ago. :D That certainly helped to make up for a lot of the trouble and aggravation.


SO......let's see the current list of reasons why I prefer Gentex over Donnelly...

1. You're not supposed to open a Donnelly mirror. Gentex mirrors can be pried apart with a credit card, or very thin/small flat head screwdriver, then snap back into place. Donnelly mirrirs are glued, or something to that effect, because they have no way to reclose. They aren't designed to be opened, and will need to be super glued back together if you take them apart.

2. The Donnelly mirrors have poor solder joints. As stated above, I had to take 3 of them apart to re-solder the 7 pins for the harness/wires to get them to function. Granted they were fine afterwards, it is rather silly to have to do this, especially in mirrors not meant to be taken apart. I've never had a problem with a Gentex mirror not functioning.

3. Donnelly mirrors are prone to breaking by leaking the auto-dimming gel. This is the biggest problem with Donnelly mirrors. Almost every car I see in the yard that's supposed to have a Donnelly mirror, it's either gone already because it's working, or still on the car because it's broken (a LOT more broken ones than missing ones). Every time I see a car that's supposed to have a Gentex mirror, it's either gone already, or nobody has gotten to it yet. I've never really seen one broken before, unless some jackass cracked the glass on purpose, or broke it taking it apart for some unknown reason (can't see what you'd be after inside one).




....that will be all for now.
 
I'd have to see exactly which mirror you have, but I do not believe so. How many pins in the harness? They're usually either 3 (early mirrors), 7 (the vast majority of them), 16 (2 rows of 8; OnStar and any mirror using the same housing as an OnStar mirror), or a lot of the newer ones are 10-pins (2 rows of 5; usually HomeLink mirrors). Most compass/temp mirrors are a dual display window. The single ones where you had to toggle back and forth between comp and temp were a very short lived mirror, and without the circuit board/buttons being designed to switch between the two, there'd be no way to get the mirror to display it.
 

Red Alert

Addict
Aug 10, 2012
696
81
I'd have to see exactly which mirror you have, but I do not believe so. How many pins in the harness? They're usually either 3 (early mirrors), 7 (the vast majority of them), 16 (2 rows of 8; OnStar and any mirror using the same housing as an OnStar mirror), or a lot of the newer ones are 10-pins (2 rows of 5; usually HomeLink mirrors). Most compass/temp mirrors are a dual display window. The single ones where you had to toggle back and forth between comp and temp were a very short lived mirror, and without the circuit board/buttons being designed to switch between the two, there'd be no way to get the mirror to display it.

It's a gentex 177 - and actually has 7 pins total. Thanks for the quick response, what you've said makes sense.
 

RareGMFan

Addict
Jan 12, 2008
934
176
Naperville, IL
Interesting write up. :bigthumb:

When one of these auto dimming mirrors goes permanently dark, do you know what the problem is with it? I had a side auto mirror that was dark on the Caddy. Glued a regular non auto mirror over it. :smile:

The outside mirrors are a whole other beast. Doesn't seem to matter which brand it is, they ALL have a much higher failure rate than the inside mirrors. I'm presuming it's due to being directly exposed to the elements for years. If any self dimming mirror permanently goes dark or yellows (depending on the year/model of mirror), it means something has gone bad with the electrochromic gel inside that creates the dimming effect. Unfortuantely, there's no way to repair that, and the mirror is shot. :(



It's a gentex 177 - and actually has 7 pins total. Thanks for the quick response, what you've said makes sense.

Ah. You threw me off when you said "pins 7-8". Yeah, that's the most common version of compass mirror used till about the mid '00s. The earliest version of compass/temp mirrors were based on that same single display, and had buttons on the bottom that said comp/temp to toggle back and forth on the display. Shortly after that, they started making them dual display.

Pins 1-3 on a 7-pin harness are pretty much universal on ALL Donnelly AND Gentex mirrors. +12, negative, and disable auto dim in reverse. The rest can vary. On mirrors with temp, 6 and 7 are usually for the temp sensor. On mirrors with map lights, 6 is tapped into a grounded source for lights, and 7 is a +12 constant to allow turning the map lights on/off individually at any time. But adding a temp sensor will not give you a temp mirror if the circuit board/buttons weren't designed for that.



raregmfan is the man when it comes to mirrors. he did one in my old GTP and it was top notch.
might have to hit you up to do one in the acura :pedobear:

Thanks, Matt. :D Anytime you're ready for that mirror, just let me know. I gotcha covered. ;)
 
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