Skoda Octavia ll 2007 VRS Estate Heated wing mirror problems.

 

Recently I have become aware that both door mirrors demisters have stopped working. Sure that it must be a fuse or relay as both mirrors did not work I decided to investigate. I always Google such problems but there was not what I would call a conclusive solution and in fact many conflicting suggestions on how they work and possible remedies.

This is how mine work. First of all there is no fuse specific to the mirrors or the rear screen demister. There is however a 40A relay 53 in location HHZG under the dash which controls the Rear Screen Demister. You can hear it click when you press the rear demister button. The Door Mirror demisters are completely independent of the rear screen demister. There is no  relay for the Mirrors on this model. (2007 Octavia ll VRS Estate).  It is possible to turn the Door Mirrors demisters On and Off with the door switch.  

The wiring and switch all appeared to be working correctly so I turned my attention to the Mirrors. I carefully removed the two wires from each Mirror glass and unclipped the OS and NS mirror. I tested the heating elements and got a stable reading of 64 Ohms on the OS and 85ohns on the NS mirror . This seemed high to me as using Ohms Law I = V/R therefore the OS mirror can only be taking a little over 200ma which is not enough to heat the mirror significantly. Purely out of interest I removed the black plastic back plate of the mirror glass and exposed the element. The element was undamaged and still perfectly bonded to the glass. I removed the element from the glass with a glue solvent.  See Pic.  The 30 vertical  black carbon  elements are connected in parallel. These have deteriorated and ceased to conduct over a period of time. As parts of the carbon track cease to conduct so the overall resistance of the mirror element increases. This causes the current to decrease thus the heat produced goes down. This is a gradual process over time in both Mirrors and therefore goes unnoticed.

 I sourced 2 new original mirrors on Ebay at a cost of £25 for both.  I tested the new mirror elements the resistance was 15 ohms for the OS and 12 ohms for the NS  hence each mirror draws approximately 1 Amp and are warm to the touch in 2mins. So if you have mirror problems start by testing the element resistance with a multimeter. It may save you some time. Incidentally both my old mirrors still looked like new with no deterioration of the silvering. Hope this Info is of help to others.

 

Ps What a great car the Octavia VRS petrol Estate is.  Just looking for my third one.

 

 

My 07 heated mirrors were also pretty much shot. I guess due to the same things.

 

I was just going to replace the glass but replaced the car instead.

Thanks nice tip, and explanation... will look at mine was only thinking the other day how useless they were.

 

Aj

Replaced both my mirror glasses last year for around £25 10 min job.

 I forgot to mention in the original post that the Mirror demisters can only be switched on while the engine is running.  Initially maximum voltage (alternator voltage around 14 volts) is applied to the Mirror demister element producing maximum heat output for initial de-icing and demisting. Within a few minutes the voltage is modulated (reduced) using Pulse Width Modulation (PWM). This results in a reduction in current and hence the heating effect is reduced. This saves power and probably considerably extends the life of the heating elements especially as most of us leave them on. It is also very possible that the modulation timing is linked to outside temperature but I am not certain of this. 

Replaced both my mirror glasses last year for around £25 10 min job.

Same here mate. The heating elements had delaminated from the rear of both my wing mirrors. I ordered two new mirrors from e bay for about the same cost that mdk 1 paid and replaced them in no time at all.

It's not a difficult job and there a few people on YouTube who will show you the way.

Good luck.