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D2 - Interior Electrics Airbags, Sensors, climate modules, instrument clusters, switches etc

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Old 27th January 2019, 09:30 AM
Dj4man Dj4man is offline
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Default 2000 S8 heated windscreen not working

Hi,

I'm 100% certain that our S8 had heated windscreen fitted as an option from factory, the screen would demist in seconds when the blowers were switched on to windscreen setting. However, after a screen replacement and seeing the fitter playing with wires attaching to the screen, the wind screen no longer demists anywhere near as quick.

I've scanned the Hvac with VCDS and all of the flap motors are working correctly.

Where is the the heated screen control unit hidden on the car and the wiring which runs to the screen, does anyone know? I'd like to try and repair this function.

The windscreen was fitted a couple of years ago now and the car has been stood for 18 months whilst i'm in the process of recommissioning it for an MOT.

Just to add that the heated screen function had stopped working before the '8 was taken off the road.

Thanks.
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Old 27th January 2019, 09:47 AM
MikkiJayne MikkiJayne is offline
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The heated front screen control module is in the boot above the battery. Its controlled by an output from the HVAC unit. Not sure where the wires run.
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Old 27th January 2019, 09:56 AM
Dj4man Dj4man is offline
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Quote:
Originally Posted by MikkiJayne View Post
The heated front screen control module is in the boot above the battery. Its controlled by an output from the HVAC unit. Not sure where the wires run.
Thanks. I'll have a look at that.

I do have issue with water getting in to the spare tyre well, so it may be something to do with that. Another job I need to rectify.

Cheers,

Dan
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Old 27th January 2019, 11:14 AM
MikkiJayne MikkiJayne is offline
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That may be the boot cable grommet where it goes in to the body on the right hand side just near the hinge. The grommet disintegrates and rain just drips in above the battery and rear light.
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Old 27th January 2019, 11:42 AM
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steamship steamship is offline
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As MJ says, the controller is in the boot, above the battery. I have a photo of it somewhere, but can't find it. It is posted on here on the forum, but it's a black plastic box maybe 10x5 inches in size and about an inch thick, with some heavy cables coming from it. There are also a few fuses just above it, though not sure if they are relevant.

As to the screen itself, I believe there are four connections to it. One in each bottom corner (can't find that photo either), which you can maybe see in the gap between the dashboard and the A-pillar. The top two you can see if you remove the lighting module up by the mirror.



EDIT: Found the picture of the module in the boot:

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2001 A8 D2 FL 3.7 Q - LPG Conversion, Engine: AKC, Gearbox:FBB, Colour:LY5X Aqua Blue pearl effect, Interior:WJ light beige/dark beige valcona leather with burr walnut inserts

My DIY jobs - Replaced alarm horn, Replaced Coolant Temp sensor, Updated RNS-D firmware, Installed Reversing Camera and Digital TV, Dashcam Installation, Retrofitted Rear Blinds, Auto-Dimming Rear View Mirror, Chrome Boot Struts

2008 S8 D3 5.2 V10 - Engine: BSM, Gearbox:KLW, Colour:L--- Suzuka Grey, Interior:Black/Black with Silver/Black valcona leather with carbon atlas inserts, Bang & Olufsen, Heated windscreen, Soft-close doors, TV, DAB, AMI, Quad Zone, Auto Boot, Auto dim Mirrors, Keyless entry, PDC with rearview camera, AFS II Headlights

My DIY jobs - Fan Jet Windscreen Washers

Last edited by steamship; 27th January 2019 at 11:52 AM. Reason: Added photo
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  #6  
Old 27th January 2019, 04:01 PM
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notorious notorious is offline
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After receiving request for heat from HVAC unit the module in the boot will check battery voltage and only after making sure the battery is fully charged it will send 42v via meaty wires to windscreen.

This is documented in ELSA and I have pasted exact logic in one of threads about heated windscreen.

So check if battery is fully charged and actually holds the charge during the heating cycle
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Last edited by notorious; 27th January 2019 at 04:05 PM.
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  #7  
Old 27th January 2019, 05:28 PM
Dj4man Dj4man is offline
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Thanks for all of the above input.

I do have the module above the battery....

I will remove the interior light and check the wiring is connected tomorrow. Along with checking the boot grommit.

I know the battery isn't the best, but it does hold its charge and I'm looking to replace it shortly after the MOT.


Thanks, Dan
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  #8  
Old 27th January 2019, 10:21 PM
paulrstaylor paulrstaylor is offline
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Quote:
Originally Posted by Dj4man View Post
after a screen replacement and seeing the fitter playing with wires attaching to the screen
Are you sure they were attached?
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