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miklosszoke 02-03-2011 01:35 PM

Auto-dimming mirror does not work
I have bought a used 2010 Focus SES with auto-dimming mirror, but it does not work at all. I have tried to cover the front sensor and used a torch to beam into the rear sensor: nothing. The corresponding fuse is ok.

Do you have an idea what to check?
I am an electrical engineer so I should be able to measure the voltage on the plug if I would have a wiring diagram.


andrewsfm 02-06-2011 08:28 PM

I can tell you that most electrical engineers make the worst phone line repair guys...

Anyways, at night park somewhere dark, sit in the drivers seat and look in the rearview, and get someone to hold a bright flashlight and shine it through the rear window onto the mirror.

With no light hitting the front sensor, and lots of light hitting the sensor facing the rear, it should start to darken slowly to a green colour.
The flashlight should look greenish in the rearview.

ChrissyL 02-12-2011 05:55 PM

^^Good step 1 in the process of elimination. If your mirror doesn't dim in less than a minute, step 2 should be checking the connectors on the wiring going into the mirror, both for physical connection and for voltage (with the car running, a VOM should show nominal system voltage from around 12.6 to around 14 volts).

To go to step 3, you'll need to access Ford's online shop manual (since there isn't a commercial manual out for 2008+ models yet). Talk to your dealer's parts or service techs to get the wiring diagram you'll need to go on to test the connections further upstream.

dadsWagon 02-13-2011 12:45 PM

Why not try :

Step 1 - Go to dealer and ask to check/fix it... it should still be under warranty


johnkos 02-13-2011 02:51 PM

I have a 2009 and it doesn't seem to dim unless the car is moving and someone is behind.

00CSVT 02-13-2011 08:24 PM

I installed an auto-dimming/compass mirror in my 07 and have installed several of them. Most of what you will find are manufactured by Gentex and the pinouts can be found online.

You should be able to unhook the connector and check to see if there is voltage across pins 1 and 2 easily enough. Also, if pin 3 has power it will disable the auto-dimming function (reverse).

Here's the typical pinout...
PIN 1 POWER +12 volts

miklosszoke 01-04-2013 01:25 PM

Thank you guys! As it turned out just the fuse was blown. Still it was $110 for the "repair"...

gsellers 01-05-2013 11:14 PM

What's behind you doesn't matter...

miklosszoke 01-06-2013 09:00 PM


Originally Posted by gsellers (Post 4527333)
What's behind you doesn't matter...

Very true, I wrote it only for those who would face the same issue. Check your fuses first before bringing the car to a mechanic!

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