Wonky speedo and now a wonky fuel gauge?

[jockthedog]

Could this be a sign of an ECU problem?

The speed sensor has been throwing codes, but today the fuel gauge started moving about randomly.

The speedo thing started at xmas when the car had been outside shivering in the rain for a few days and has persisted, on and off.

Now it's back in the garage and taking a look under the scuttle, there may be a mouse or a bird living in there, from all the leaves etc!
Some water in the scuttle but not a huge amount. I'll give the holes a poke when it's light.

I'll dyson it all out tomorrow, but has anyone else had wonky gauges like this? Speedo went haywire and then just read zero.
Fuel level dropped from full to half to 3/4 to full again.

[ChrisRS6]

If the scuttle is full of leaves, check the passenger carpet for dampness.

If water couldn't drain, it can leak into the cabin through the pollen filter. If it gets in, there are some electrickery jiggery pokery important boxes on the passenger floor.

If these get wet, they can cause all sorts of mischief!

...but could be something else entirely!

[bam_bam]

Check both nearside footwells. The front passenger footwell never filled in mine but the rear did.

[Shoppinit]

Could be bad fuel level sender or its electrical contacts.

Could be bad VSS sender or its wiring.

Maybe it's humidity damage to the dash pod.

Vagcom will tell you what the cluster is receiving and help you determine whether it's an issue with it or not.

[jockthedog]

vdcs was saying that the speed sensor had short-to-ground or suchlike, more than once.

I've not checked since the fuel gauge thing (too coincidental surely), but there is a pile of mushy leaves tucked right behind the ecu box, where I can't get at it.

Does look like it was a mouse nest, with a few tiny acorn shells and leaves and twigs. Can't all have got down the side of the wiper! Not acorn shells.

It was too blizzardy to open the ecu box today, but that's my best guess. Mouse-related over-mulching of the ecu.

The scuttle drained the half inch of water that was in there when I prodded the hole under the coolant res. Is there another unreachable drain hole under the enormous brake master cylinder?
If there is, it's a little blocked too. Another half inch of water on that side.

Pollen filter was dry, as were the carpets.

If it ever stops snowing I'll grab the latest codes.

[Shoppinit]

I'm pretty sure the fuel gauge sender goes straight to the cluster without passing near the ECU.

You'd think after all these years building cars Audi would have figured out how to keep the water on the outside of the car.

[jockthedog]

Had a heap of fun this morning.

I took the plunge and removed the wipers which were of course corroded-on a little (a mole grip can make a handy press tool, if you dont have a small enough puller)

Managed to unclip the lower window surround (pain to get back in but when it's in, you can see how good a job it does)

And thus get to the back of the ecu box.
In fact I loosened the wiper motor brackets etc too, to move it out of the way.
Wish I'd taken a photo, but yes, definitely looked like a home to a mouse, squirrel or small bird at some point.

Water coming in thru the corner of the window surround and down the side of the wiper was pooling behind the ECU, thanks to this nest, instead of draining down into the scuttle.
I'm hoping that is what was causing the problems with the fuel gauge.

I never did find that other drain plug, even with a borescope!

Or at least I didn't think I had, but I did get a good puddle under the car when I looked and I eventually dyson'd the whole area clean, dried it with a hot air gun and then dyson'd again before replacing everything.
Dod of grease on the wiper shafts to save time next time.

VCDS didn't mention the fuel gauge or any inst cluster issues.
And the first time the speed sensor was faulty was 2014, before my ownership, so I'll need to see to that.
I have a spare one sitting here ready to go, in fact.