Heated Mirror Fault

[Westyfield2]

One of the heated door mirrors on my C7 Avant has stopped working. Other is working perfectly fine.
Did a VCDS scan and it came up with:

1 Fault Found:
00920 - Heated Outside Mirrors; Driver Side (Z4) / Passenger Side (Z5) 
            012 - Electrical Fault in Circuit
             Freeze Frame:
                    Fault Status: 01101100
                    Fault Priority: 3
                    Fault Frequency: 1
                    Reset counter: 135
                    Mileage: 69755 km
                    Time Indication: 0
                    Date: 2016.11.18
                    Time: 18:11:24

I've popped the Mirror glass off and stuck a multimeter on the cables.
On the working mirror it's what you'd expect; 0v when off and 12v when turned on.
On the broken mirror it's a constant 4.5v, with no change when the heater is turned off or on.


So, any suggestions?
My next guess is to trace the cable back further to see if it's getting 12v at an earlier connection, and my guesses on the break location would be where the mirror bolts on to the door (in the folding hinge), or where the door bolts on to the car body.

[Vmax211]

If the mirror is getting 4.5V, there probably isn't a break in the wire. It seems to me to be more likely a problem with the controller, wherever that is.

[staman_sk]

3 years ago, but, how did u fixed it ?

I had the very same problem and my case was the faulty heated pad. Once I disconnected the plugs from the faulty mirror pad, cleaned the connectors I could once again see 12V.
My case was a heated pad that was faulty! it's a circuit and you HAVE TO HAVE some impedance on it. Typically is about 5 Ohms

If you see 0 Ohms = you have a faulty heated pad (that was my scenario)
This was my case too. Visited dealer and been told, 500EUR for brand new 4G0857535E / 4G0857536E (this is a heated autodimmed version).
Not sure about US price but here in Europe, 500EUR .. painfull for such a small piece of glass!

I was very uhnappy about it. My glass was in absolutly perfect condition, autodimmed function was working great, just that silly heating was faulty.
There are cheap aftermarket replica mirrors with heated functionality* but there is NO single model with heated + autodimmed feature.

I've spend lot of time trying to find a solution for this, ended up this way:


My heated glass is fixed now, working as original one .. and for less than 1/10 of the price I would have to pay

*explained very well in that video

[isaacmaple08]

I realize this is almost a year later, and 4 years from the original post, but I found out what always seems to break are the actual Electrical connectors. I removed, resoldered, and reglued them and they work great 4.9Ohm & 14.4v ~ 40w of heat. The chinese ones (without autodim) seem to have a much higher Resistance and lower wattage.

In the meantime of fixing them I bought another heated + autodim mirror from a Junkyard for $35. Mine was needed for a Q7, but the ones I purchased were for a Q5 but seem to be interchangeable with a lot of models.

"Зеркальный элемент Audi Q5 8R0857535F"

If you have a friend that knows how to solder, or a hobby shop near you, they can do this for about $20 I'd guess in the case that you can't find the piece from a junkyard, OLX or Craigslist.

May just be my cheap nature but I couldn't bring myself to pay $500 for some piece of glass with an electrical current running through it.

20211225_095950.jpg

[Audisthesia]

Yes, these terminals are exposed to the weather elements and get wet easily. I've changed several mirrors & turn indicators on the mirrors on multiple VAG cars... They all have the same exposed terminals. My advice, if you take the sideview mirror glass off for any reason, put the anti-corrosion spray/lube/sealer/etc of your choice on them when you reinstall the glass to try and prevent this.

[WatchMeSpend]

And people wonder why I have "mirror mitts" for when the car is getting snowed on....