Troubleshooting rear view mirror

[328ioc]

So I have always thought something might be up with my mirror in my car because it never seemed to auto dim very much.

Then I caught an episode of Wheeler Dealers where they bought an E39 M5 and had to replace the rear view because it had the fluid mark.

Once installed they covered the light sensor on the back of the mirror to test the auto dimming and obviously it dimmed.

I have done this with my mirror and I get no dimming at all. Is there anything else besides the sensor that can break? Or should I just replace the Mirror and be done with it?

[Oli77]

I have had the same issue since the day I purchased the car. I took the mirror apart, made sure no wires were cut or damaged (could not find anything obviously wrong). I Made sure it was not a fuse. Your mirror never lost its fluid and it looks fine?

Sorry, I am no help (but would like to find out from others).

[328ioc]

Don't worry about it, you actually did help because I forgot to mention that no my mirror has never lost its fluid as far as I can tell and it looks totally fine.

[Oli77]

Okay, we're in the same boat then.

[328ioc]

Yeah its starting to really bug me because glare really bothers me at night. Tinted windows helped a little but its still a pain.

[derbo]

Pin 3 and Pin 10 are the two power wires on the mirror itself.

If you look closely at the plug on the mirror you can see labels of the numbers on the side of the plug. Pin 3 is the power (Switch 12V Green/yellow?) and Pin 10 is ground (brown wire)


1 2 3 4 5
6 7 8 9 10



To perform an autodim test. Make sure you cover the rear photo resistor sensor. Shine a flashlight on the photoresistor sensor in the front and you should see the mirror turn green/blue. If it doesn't, make sure you have power to those pins. I tested it out with a small 12V power supply to make sure the autodimming worked before I retrofitted it in.

Double check you have power in pin 3 on the plug on the harness. You can check with a multimeter to see if it sees 12V when the key is switched on.

I don't know what else to check if it doesn't autodim besides that..

[Oli77]

Thanks for the pin info derbo. I will open the sucker up and see if I haz power there.

I tried the test with the flash light, no go for me.

[328ioc]

+1 Thanks for the info. I will try it as well.

[derbo]

hopefully it helps. I'm curious whats wrong!

[328ioc]

Been crazy busy with school, hopefully I can check it this weekend and update!