Light and rain sensor retrofit

bigsmall

Registered User
I was hoping to retrofit the light and rain sensor for my A3. I would just like to check first, do I just need the sensor and the headlight switch with auto position? And will it need re-coding with VCDS or similar to work properly?

Also, I have seen various kits available for purchase, including some on ebay. Some of them say they are only compatible with LED headlights (I have Xenon). Is this just because there are different version of the headlight switch?

Finally - what is the difference between the 8V0 941 531 G and the 8V0 941 531 AR switches? They are both showing as compatible with my A3 8VA, and look exactly the same.

Thanks!
 
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Rcord

Registered User
I think I had the same questions when I retrofitted light/rain sensor on my A3. Almost gave up at first because I've read on Kufatec and other websites that in order to install the sensor I would also have to replace the windshield! So I took my car to a local Audi dealership and asked them if they could do such retrofit and they sait it would be impossible, and it would be necessary to replace the windshield, etc. Nothing of these was true. Actually, the windshield in my A3 had the proper mount for the sensor (and rearview mirror), which was occupied by a cover that has the same shape and metal clips of a sensor. I've never seen a A3 that seemed to be different from mine, but I think you should make sure yours is also ready for the sensor, as in the picture below (cover part number 8V0907613 fitted in the sensor's place, with rearview mirror removed):

CAM01879.jpg



I was hoping to retrofit the light and rain sensor for my A3. I would just like to check first, do I just need the sensor and the headlight switch with auto position? And will it need re-coding with VCDS or similar to work properly?

Yes, you will need to code the sensor.

Also, I have seen various kits available for purchase, including some on ebay. Some of them say they are only compatible with LED headlights (I have Xenon). Is this just because there are different version of the headlight switch?

Finally - what is the difference between the 8V0 941 531 G and the 8V0 941 531 AR switches? They are both showing as compatible with my A3 8VA, and look exactly the same.

Thanks!
It seems that those part numbers refer to switches that have the "all weather lights" button instead of the front fog lights (the symbol on the buttonis different) and also a knob to adjust the headlights level, which doesn't apply to Xenon headlights that have auto adjustment. Does your A3 have front fog lights? The features present in your car will determine the correct light switch unit.
 

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bigsmall

Registered User
@Rcord That's really helpful, thank you. Just to clarify, as you had the mount ready to accept the rain sensor, did you have to also replace the loom, or not?

I looked into the switches more, and with the help of my handbook I figured out that I need the 8V0941531AE switch:

iwFjYJ6m.jpg



That has both fog switches (the one with the rain logo is for LED lights), the auto position, but no dip adjustment (which is only for halogens).
 

Rcord

Registered User
Just to clarify, as you had the mount ready to accept the rain sensor, did you have to also replace the loom, or not?
The picture you posted is just like the unit I used. Actually, my car didn't have the front fog lights either, so I did both retrofits at once (light/rain sensor and fog lights) so I would't have to replace the light switches again. My car had no loom installed but the rain sensor kit had the loom included.
 

bigsmall

Registered User
The picture you posted is just like the unit I used. Actually, my car didn't have the front fog lights either, so I did both retrofits at once (light/rain sensor and fog lights) so I would't have to replace the light switches again. My car had no loom installed but the rain sensor kit had the loom included.
Okay I see. I've been looking at buying the sensor and found some cheapish ones on ebay, but they don't come with the loom. But Kufatec has the loom for £24, so I would probably go for that.

One more question - did you replace/install a gel pad when you fitted the sensor? If so, was it the round one or the teardrop shape? Cheers.
 

Rcord

Registered User
One more question - did you replace/install a gel pad when you fitted the sensor? If so, was it the round one or the teardrop shape? Cheers.

The sensor must have a gel pad included (and a plastic piece protecting the pad) so you will not have to worry about it, except if you buy it used, which I don't recommend. It seems that gel pad replacements are expensive compared to the price of a brand new sensor. The cover installed in the car has no gel pad so you don't have to worry about how to remove it.
 

bigsmall

Registered User
Just a quick update on this. I found out by checking the PR codes that I actually have halogen headlights, so I will need the switch with the dip adjustment (8V0 941 531 AJ).

Also, I took the mirror off, and found I already have a sensor there - 8UO 955 559 (humidity sensor). That must be because I have climate control. So I'll need to swap out that sensor for a humidity, rain and light sensor (8U0 955 559 B).

2O19yg0l.jpg


So now what I'm not sure about is, will the cable that is already there support the new sensor, or will I need to replace it? And if it needs replacing, is there any info on where the connections are located? See below for the cable:

yyjftmQl.jpg
 
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Rcord

Registered User
Also, I took the mirror off, and found I already have a sensor there - 8UO 955 559 (humidity sensor). That must be because I have climate control. So I'll need to swap out that sensor for a humidity, rain and light sensor (8U0 955 559 B).

So now what I'm not sure about is, will the cable that is already there support the new sensor, or will I need to replace it? And if it needs replacing, is there any info on where the connections are located? See below for the cable:

I remember reading a post on the forum with a case just like yours, no light/rain sensor with a humidity sensor instead. You'll probably find the posts with a search. In my case there was no sensor at all and no wiring loom and I thought it was a little nonsensical configuration for Audi as a form of cost saving, but I'ts beyond my understanding why would Audi not install a complete sensor when there is a complete wiring installed. If installed from factory, the costs wouldn't significantly change with the choice of one type of sensor or another and with an aditional "AUTO" position in the light switch. For the customers however the costs are much higher since they have to replace sensor and light switch by new ones.

I've checked the wiring diagrams and it seems to be the same for both types of sensors. You don't need a new loom.
pin 1 - grey/purple wire (positive connection)
pin 2 - brown wire (earth connection)
pin 3 - green/purple wire (LIN bus - connects to T73c/28 on J519 and to pin 1 on ligh switch connector)

So it seems that you will be spared from the most complex of routing a new harness and making the connections. Hope you still didn't order the loom.
 

Rcord

Registered User
P.S.: Though you don't have to change anything on the car wiring, only replace the sensor and light switch, you still have to do some coding on sensor and switch. Also, in case you want to use the coming home/leaving home feature for the lights or the automatic rain closing for the windows, there is some more coding to be done on the central electronics. All easy to do if you have access to VCDS, or can get help from someone who has.
 

bigsmall

Registered User
@Rcord: thanks for the info - that's good news! I only ordered the sensor and switch, so all is good. I'm considering getting a VCDS cable, as there a few things I want to change anyway. I did message some people from the map, but haven't heard anything back yet.
 

bigsmall

Registered User
I retrofitted the rain and light sensor and a new headlight switch (with auto position) on an Audi A3 8V. The sensor is working fine, as are the auto headlights and wipers.

What I'm not sure about, is that the instrument lighting is now constantly on (regardless of the headlight switch position), and its brightness is not being altered by the adjustment knob on the headlight switch. I'm not sure if this is a coding thing, a 'feature', or a physical problem with the switch.

I used the following coding after fitting the headlight switch:

Code:
Select Module 09 (vehicle electrical system)
Select coding -> function 07
Byte 6
Activate bit 1

Byte 7
Activate bit 5

I can also post the full coding from the car later, if necessary (don't have my cable with me at the moment). I was just hoping to get some feedback about whether anyone has seen this before, so as to inform my next steps in fault-finding.
 

Rcord

Registered User
It seems that you coded the options on BCM but still didn't code the sensor itself. If you are using VCDS, in "module 09" you can select the sensor in the first screen (it will appear identified as 8U0 955 559 B) then use the helper to select the appropriate options. Pretty simple. My current setting is "07006C" but I have automatc rain closing set and yours will be different if you don't want to set this feature on.
 

DJAlix

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00006C is factory coding for the Audi A/S/RS3
 

kpm278

Registered User
I got a new rain sensor today complete with plastic cap. There's a bit of dust on the gel pad. How much is too much dust - should it be cleaned with soap first or will that kill the adhesion?
 

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bigsmall

Registered User
I got a new rain sensor today complete with plastic cap. There's a bit of dust on the gel pad. How much is too much dust - should it be cleaned with soap first or will that kill the adhesion?

Mine also had some dust on the gel pad. When I looked in Elsawin at the installation manual, it says there's a specific product for cleaning the surface of the gel pad before installation. I couldn't find the right product to buy, and didn't want to risk trying something random, so I just very carefully picked off the large bits with a needle. I'm not suggesting this is a sensible plan, but my new sensor worked fine.
 

DJAlix

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Need to make sure that the highlighted sensor window is dust free for correct operation. I have retrofitted a few of these and use both "low tack" and "medium tack" sticky tape in order to remove any dust. Double it back on itself and dab away until the dust is gone, much like you would when applying a laptop or mobile device screen protector.

IMG_3209.JPG
 

Scott Kitterringham

Registered User
Does any body no which rain / light sensor I will need I’m A3 8v with god lights and climate control

I have bought a b but not sure if I will been a c

Can’t see where to find the info
 

DJAlix

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Does any body no which rain / light sensor I will need I’m A3 8v with god lights and climate control

I have bought a b but not sure if I will been a c

Can’t see where to find the info
I would go:

B = MY 2013 to MY 2016
C = MY 2017 to present
 

DJAlix

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Wezango

Registered User
Hi! I retrofitted light&rain sensor (8U0 955 559 C) to my 2017 A3. I did all the things needed in VCDS and right now automatic wipers work fine, coming home leaving home works also fine (lights turn on when it's dark and doesn't during a day) but automatic lights seems to be always on low beam and never turn to just DRL At the same time I lock the car and coming home doesn't turn on lights because it's bright enough outside. Sure I changed my light switch with a new one. Light sensor seems to be working ok, because coming/leaving home works as intended. Is there some VCDS command I missed?
 

DJAlix

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Hi! I retrofitted light&rain sensor (8U0 955 559 C) to my 2017 A3. I did all the things needed in VCDS and right now automatic wipers work fine, coming home leaving home works also fine (lights turn on when it's dark and doesn't during a day) but automatic lights seems to be always on low beam and never turn to just DRL At the same time I lock the car and coming home doesn't turn on lights because it's bright enough outside. Sure I changed my light switch with a new one. Light sensor seems to be working ok, because coming/leaving home works as intended. Is there some VCDS command I missed?
Need to know the steps taken / completed in order to assist.
 

maxx16v

New Member
VCDS Map User
A bit of an old thread however I came across this on my travels......
8V0941531L 5PR
SUPERSEDES TO
8V0941531AE 5PR
but the problem is that it is NOT for halogen lights...so if the car has optional equipment / PR codes as listed below it may work if not its not going to work at all.

A3 2013-14 MODEL YEARS (8V) - WITH PR NUMBERS 8IG, 8IM+8N6+8WB OR WITH PR NUMBERS 8ID+8N6+8Q0+8WB

A3 2015-16 MODEL YEARS (8V) - WITH PR NUMBERS 0K0, 0K2, 8IG, 8IM+8N6+8WB OR WITH PR NUMBERS 0K0, 0K2 8ID+8N6+8Q0+8WB

A3 2015-16 MODEL YEARS (8V) - WITH PR NUMBERS 0K3, 8IG, 8IM+8N6+8WB OR WITH PR NUMBERS 0K3, 8ID+8N6+8Q0+8WB
A3 CABRIOLET 2015-16 MODEL YEARS (8V) - WITH PR NUMBERS 8IG, 8IM+8N6+8WB.

I have the halogen lights and none of the above PR numbers so I think its not going to work on my car but I do stand to be corrected
 

Crash2010

Registered User
Sorry to re open old thread but thought instead of making new post i’d highlight here.

Thinking of doing this retrofit and have gathered that i would need sensor(8U0955559B) since i got auto climate control and the headlight switch(8v941531AE) Since i got xenons with front fog lights.
where can i source the sensor brand new? Found some cheap used but want to know how much new ones cost. Can anyone also help me with the gelpad? Struggling to find a place that sells it. Any help is appreciated
 
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kpm278

Registered User
Got mine from ebay, non genuine, £38 with gel pad back in 2018. I have the full auto climate control and 2014 car and fitted the C part. If you’re quick there’s a genuine Audi part for £50.

https://www.ebay.co.uk/itm/264529462706

If it doesn’t come with a gel pad places like autoglass have them, if you find a friendly fitter......
 
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Crash2010

Registered User

CanadaA3wales

Canadian living in South Wales - Audi A3 8V 150BHP
Can I ask a simple question please?
I bought a 2014 basic Audi for very cheap and just adding little bits I want and need to it.

With this, I thought you needed a switch like the VW to turn on and off the Auto sensor, if so where do you install it?

Is this a easy retro fit?

I am installing a reverse camera next, but that can wait. I know how to reverse lol
 

mpw2081

Registered User
Can I ask a simple question please?
I bought a 2014 basic Audi for very cheap and just adding little bits I want and need to it.

With this, I thought you needed a switch like the VW to turn on and off the Auto sensor, if so where do you install it?

Is this a easy retro fit?

I am installing a reverse camera next, but that can wait. I know how to reverse lol


Mate in same boat as yourself. My wife's car could do with these fitted and looking for somebody in northwest who could fit and supply. Any members can you please help, I am useless at this type of stuff.
 

kpm278

Registered User
You need to replace the light switch with one that has ‘auto’ on it. For the wipers you just set it to intermittent and this acts as auto.

Can I ask a simple question please?
I bought a 2014 basic Audi for very cheap and just adding little bits I want and need to it.

With this, I thought you needed a switch like the VW to turn on and off the Auto sensor, if so where do you install it?

Is this a easy retro fit?

I am installing a reverse camera next, but that can wait. I know how to reverse lol
 

mpw2081

Registered User
You need to replace the light switch with one that has ‘auto’ on it. For the wipers you just set it to intermittent and this acts as auto.

I was under impression coding needed and maybe a different sensor
 
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