Insight into BMW's Donnelly Failed Rear View Mirrors

[Scott@Radar-Mirror.com]

If you own select BMW models produced before 2008 and haven't experienced a rear view mirror failure chances are good that you will down the road. I've owned a E46 M3 since 2004 and my mirror failed twice - I've been working on these mirrors for 10+ years now and thought I'd share some info about how the mirrors work, why the Donnelly mirrors fail and why we hope you will choose us if your mirror needs to be repaired.

The first version of an auto dimming mirror was actually a prismatic mirror (the tilt mirror everyone had before auto dimming) - there was a light sensor on the mirror and a small motor inside the mirror that automatically tilted the mirror up and down. The mirrors were only available on very expensive cars for the time and became obsolete when the electrochromic auto dimming mirrors were developed. BMW was among some of the first car manufacturers to offer the mirrors on their cars.

There are two companies that produce the auto dimming mirrors for 99% of the car manufactures around the world. Magna Donnelly is one and Gentex is the other. The companies actually originated from the same family and are both headquartered in Holland, MI. When the electrochromic mirrors were first made available Magna had the lion's share of the business - over time primarily due to the overwhelming number of mirrors that failed Gentex has emerged as the leader and now enjoys (I'm guessing) 80% of the auto dimming mirror business. The mirrors they produce have not had the issues that the Magna mirrors do - BMW jumped ship around 2007 and moved all of their business to Gentex.

What is an electrochromic mirror and how does it work?

An auto dimming mirror is comprised of two pieces of glass that are slightly overlapped on the edges, sealed together and have a transparent conductive gel or fluid injected between the layers of glass. A mirror coating is applied to the rear portion of the glass and when a very low voltage is applied to the overlapped edges of the glass the gel darkens and reduces the amount of light transmitted and eliminates glare.







An electronic circuit board is attached to the rear of the mirror with wire leads soldered to the edges of the glass. There are two photocells (light sensors) - one facing out the front windshield and one facing the rear of the car. If a sufficient amount of light is hitting the forward facing sensor the mirror will conclude that it's daytime and will not dim the glass, regardless of what the rear facing sensor sees. As it starts to get dark outside the forward sensor sees less light - concludes it's nightime and when the rear facing sensors sees any light behind the car the voltage flow is opened and the mirror begins to dim. The level of dimming is determined by the combination of light levels the two sensors are detecting.





How do the mirrors fail?

The failure of the mirrors is due to a manufacturing defect by Magna/Donnelly. The mirrors are sealed along the edges of glass and over time the seal breaks down and eventually fails, allowing the fluid to escape which is replaced by air. The amount of fluid that escapes and whether it begins to leak depends on where the seal breach is located. If the seal fails on the bottom of the mirror the fluid is going to escape a lot more quickly than if it's on the top. In most cases it takes a few years for the seal to fail - the environment that the car is in can have an impact on how long the mirrors last. Heat is known to accelerate the process so if you live in a hot climate and park your car outside in the sun for extended periods your mirror is going to fail sooner. From the pictures below you can clearly see where the seal failed on this mirror - with a small amount of pressure the two pieces of glass completely separate.







Why have so many of the mirrors manufactured by Magna/Donnelly failed over an extended period of time? Why wouldn't they have resolved this a long time ago?

This is the million dollar question. We repair multiple mirrors every day and the mirrors range from Jaguars built in the mid to late 90's all the way to Lamborghinis built as recently as 2008. I know Magna has struggled with this issue over an extended period of time and continues to make changes to their manufacturing process. They may have the issue resolved at this point but only time will tell.

What about the mirror repairs from Radar-Mirror.com? How reliable are your replacement mirrors?

We have repaired thousands of mirrors at this point and we have yet to see one of our mirrors fail due to a seal breach. The only failures that have been reported to us were due to the glass cracking and there have only been a handful of these.

We appreciate the business and kind comments we've received from this forum and look forward to serving others as the need arises. :thumbsup2:

[E86Z]

Do you do side mirrors?

[Scott@Radar-Mirror.com]

Originally Posted by E86Z

Do you do side mirrors?

Sorry not yet.. working on it. The side mirrors are a lot more complicated b/c they have to be protected from the weather. Hope to have this available soon.