I would be pretty sure its the F125. Mine is OK sometimes but selecting R will, on occasion, cause it to light up. It will clear if I stop/start and is generally fine in D. BUT "S" wont light up unless I jiggle the gearstick. I believe all my symptoms are those of F125 failure.

well decide I had better look at this myself so ~I know where everything is and what to do ; jacked up ,front wheel off , wooden blocks under for safety , found the connector on a bracket , couldn't undo the connector

finally undid the bracket the connector is mounted on and then found one half of the connector is held on by a clip so held clip open and levered open with flat bladed screwdriver ...easy when you know how
both sides of the connector nice and clean
had a hunt on my neighbours workbench and found a WD 40 product described as non silicon lubricant suitable for using on electrical equipment including circuit boards ; gave a good spray on both sides and then used the airline jet to remove excess then reassembled

tested transmission and removed fault code had a test run .......and no fault code

so far , so good

if someone had told me that the forward half was held on by a clip would have done it in half the time !

I could have told you that having spent some time figuring it out myself. But hey, its more fun letting someone else feel the pain!! :ROFL: I hope the solution works for you. It did for me for a day but then the symptoms came back. As I said earlier, quite why cleaning it will solve the apparent issue but all the time its the switch at fault is a mite perplexing.

P.S. Just how many different types of electrical connectors can there be on a car like this? Every one is different!

gee thanks david

:p

honi soit qui mal y pense :tuttut:

The switch was replaced whilst the garage was doing the control arms. It was described as a "difficult" job with one of the bolts very reluctant to come out. All now seems to operate as it should. Out of interest i decided to take the switch apart so drilled out the rivets holding the plastic case on and found that one of the contacts was distinctly dodgy. I have no idea what that contactor does but it doesnt seem to have been doing it very well. It looks dark as if there has been some arcing and the tip of the contact was, if not missing considerably shorterthan the others. Funny thing tho' is that its the one with the least contact strip to act on. Perhaps that WHY it failed.
The whiteish gunk is just lubricant. Note that this is the 10pin rectangular plug and not the older 8pin round type as shown in the Audipages article.
The garage pointed out that the lead on the new switch was some 25mm shorter than the one removed and only just fitted when taking into account keeping it clear of the exhaust!

Now that is REALLY interesting. Thanks for opening it up. +++
I always wondered what the F125 switch did and "guessed" it translated the physical position of the gearbox internals into an electrical signal for the TCU etc. to interpret and act on.
That appears to be exactly what it does and given my odd symptoms I'm now more determined than ever to get mine replaced.

Can you say how much work was involved (and cost?) and if they needed (As Adrian and my local indie suggest) that they needed to drop the gearbox a bit to get at it?

I havent had the bill for it yet as, while they doing the arms they noticed a tie rod end had movement in it for which I have ordered the part - due next week - and so final totalling up is on hold - for now! The switch was £155ish + VAT and the hours are probably about 4 (I hope!!). The Audi page guide (which I gave the garage) involves removing the transmission mount and levering the exhaust out the way - its not easy to access it and its not something you can without a lift.
I will post the detailed cost info when I get the bill :-(

I note that the part number is 01V 919 821B whereas the reference I have is 01L 919 821B, if that is significant?
Or is it just the current revision?

They show up as different parts, but both compatible with different generations of '8.

01L919821B is for gearbox codes FUM, FUU, FSG, FBE, FBG (mine is the last of these)

01V919821B is for gearbox codes APR, AQD, AFB, AKN, AQG, AKE, AKC and AMX

I guess the cable length could be the only difference?