I am sure you
are here reading this because your current SOS rearview mirror has
failed. You may have experienced some of the following symptoms of your
rearview mirror:
- Mirror is no longer dimming
- Mirror has a yellow tinge to it
- There are patches or bubbles in the glass
- Tide line or variations in colour
- Dust behind the glass
- Halo effect or inner circle present
- Mirror has leaked. Damage to the mirror casing or interior trim
How an Auto-dimming mirror
works:
An auto-dimming mirror is comprised of two
pieces of glass that are sealed together along the edges and then metal contact
strips attached to both edges.
An
electronic circuit board is attached to the rear of the mirror with a wire
soldered to teach of the contact strips.
A
conductive liquid is then injected and completely fills the area between
the two pieces of glass and then sealed at the injection point. The back of the
glass is coated with a silver mirror coating and under normal (non dimming)
conditions the fluid is completely invisible and transparent. It works just
like a normal mirror should, reflecting all light. The mirror housing contains
the electronic circuit board and photo-sensors that measure ambient light, one
facing toward the front of the car and one facing out towards the rear window.
The forward facing sensor tells the mirror whether it's day or night and
enables or disables the auto dimming function accordingly. 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 at all, regardless of what the
rear facing sensor sees. When the front facing sensor see reduced levels of
light the electronic circuit board will begin applying very low levels of
voltage to each piece of glass and the conductive fluid will begin to darken.
The level of tinting is varied almost infinitely depending on the
conditions. At night the mirror will be
dimmer than during the day, however, when the rear facing sensor detects light
(from a cars headlights behind) the mirror will actually dim even darker. This
effectively reduces the amount of light that hits the mirror coating and
eliminates glare. You may also notice your mirror dims if you drive under tree
covered roads or through a dark tunnel.
The level of dimming is constantly adjusted depending on light
conditions. Another neat trick, is that if you put your car in to reverse at
night, the mirror automatically un-dims, so that you can see where you are
going! It’s all rather clever really!
Unfortunately there was an issue with manufacture of
these original mirrors which causes them to fail. They will all fail
sooner or later. It is more 'When' the mirror will fail rather than 'If'
the mirror will fail. Due to the poor original design, when the mirror
fails it can cause devastating permanent damage. There is a (dimming)
fluid sandwiched between two pieces of glass and this liquid is highly
corrosive. When the mirror fails it can allow this liquid to leak out.
When it leaks out the glass it will eat its way through your mirror
casing and then damage anything it drips on to. I have have had unlucky
customers who have had centre consoles damaged, gear knobs, seats and
even a dashboard. It all depends on what the fluid leaks on when it
drips out the mirror. This can make it a very expensive failure indeed.
Especially if you need a new mirror too. A new mirror from BMW is over
£400 and still uses the same (flawed) technology as the original. Some
customers look to buy another second hand mirror as a replacement,
however these carry the same risks of failing as the original. It isn't
worth the risk. Your best option is to repair your current mirror only
replacing the part at fault, the dimming glass unit. This is where I can
help you.......
If your mirror has any of the above symptoms;
the best thing you can do it remove it from your car straight away.
Please bear in mind if you have a Convertible M3; by removing your
rearview mirror some functions will stop working. You will no longer be
able to lock your car with the remote fob. The central locking will no
longer function and neither will the alarm. You can still lock the car
manually using your key until the mirror is repaired and refitted in the
car. If you have a Coupe, everything will still work as normal even
with the mirror unplugged.
Once you have removed your mirror, I
recommend following my DIY guide to strip the mirror down and remove the
defective glass unit. This will minimise any damage potentially caused
by the leaking fluid. The DIY guide to remove the mirror from your car
and carry out the full repair is located on my website here:
mirrorjohn.com/How_To_Fix.php