D2 S8 20" Wheel ABS Sensor Repair
 

Yes, I said repair which is a little odd but allow me to give some details.

My D2 S8 has the 20" wheels and that has a special ABS sensor that is not the standard unit as many of you will know. A normal A8 ABS sensor can be bought for about £10, the 20" Wheel version for the S8 is £170 from TPS/ Dealers/ eBay and even second hand is expensive.

So what to do :rolleyes:

4D0927803E is the part number and I did not want to spend all that money and second hand is not worth it in my mind on a sensor. Hence I went on the hunt for something I could use from another VAG model that would work.

It took some time but I spent a whole £9 on one of these from eBay:

https://www.ebay.co.uk/itm/ABS-WHEEL...53.m2749.l2649

Its a B6 A4 unit part number 8E0927803A, it looked the same sensor from the picture so I though why not just give it a try.

The photo below shows the original S8 one on the right and the new A4 one on the left.

http://forum.a8parts.co.uk/picture.p...pictureid=1147

Yep, looks and fits perfectly. Sensor itself has the same dimensions, the only difference is the mounting plate is a little deeper so you need a longer bolt to hold it in.

Now the wiring harness is NOT THE SAME, therefore you need to cut the ABS sensor off it, do the same with the original S8 harness and solder the new sensor on and put some heat shrink on it. Hence why I called this a repair as you do need to cut/ strip/ solder to make up the old harness with the new sensor.

The result, works perfectly and looking at the measuring blocks on VAGCOM the readings are all good also.

£161 saved +++

Great find +++

I've been looking (not very hard) for an alternative sensor for these - so far tried just the TT and D3 which aren't quite right. I will have to acquire a B6 one and give that a go :)

Interesting. 2 questions.

What was the problem you were fixing?

Why is the 20" wheel one difference?

D2s which had factory 20" wheels have steel struts with larger wheel bearings whereas the non-20" FL cars have alloy struts. The ABS sensor for the steel strut is unique and genuine only so heinously expensive.

By strut do you mean hub?

If you like yes. I call the bit that the control arms bolt to the strut or upright, and the turny bit the hub, but they are generally interchangeable :) Technically upright is probably more correct since its double wishbone rather than macpherson strut.

It was being replaced as it had failed, thrown a code and was no longer sending a speed reading.

Yes upright, that's what I meant. We got there eventually :)

Must check what mine are

So there's obviously a reason for this, but what is it and what are the downsides of fitting FE 20" wheels to a car with non-FE alloy suspension?

Or were they just using up the stock of some suspension variant made maybe for the armoured vehicle or some other rare special option?

I honestly don't know. It is totally counter-productive to handling and ride comfort to fit heavy 20" wheels and then to couple them with even heavier steel uprights which weigh 5Kg more each than the alloy ones. They were specially produced for the 20" cars rather than something which needed using up and are available in both Brembo and HP2 brake fitment.

I can only surmise that something in the load calculations suggested that the alloy upright would not take the stresses of the 20" wheel (or for that matter the 3.3 V8 TDI) and so they designed new uprights from steel instead, and put the larger 92mm bearing in them.

The lower arms are also different for the steel struts - the lower rear has a different inner bush. Possibly stronger?

People have been running 20" wheels with alloy uprights for many years and they are absolutely fine. Whatever calculation it was, there is clearly a substantial safety margin in the alloy stuff. Its probably an extreme use case which no one will ever actually encounter.