Another fuel gauge problem...

[rharris]

Hi all,
Anyone seen this before and no what the problem is? When the car has around 3/4 tank of fuel the gauge starts paying erratically. Settles down when the fuel levels gets to about half way. They've tried a firmware update (apparently a possible issue) but that has not changed the situation, my own guess is a fuel sender issue.

Thoughts?

Btw, its a '05 3.0 Quattro (Diesel)

[towcestervag]

you should be able to check the guage using final control diagnosis
then you could check the sender manually if need be

[a8 tech]

This is early 4f model then the wiring in the tank is the likely cause in some cases the signal wire for the senders breaks but its cable tied to the pump and only by pulling the wire can the break be seen as the wire still has continuity because its not fully separated then the resistance values are still read by the dash but they are inaccurate and the movement of the float can move the wire therefore altering the resistance further,using a good resistance check its easily confirmed what's going on as well as final control but the tank is the place to look and don't be to surprised if the senders require replacement.The sw update for earlier 4f dash pods relates to slow responses from the fuel gauge after the tank was filled to maximum

[rharris]

Thanks a8 tech; I wasn't convinced it was s/w as I'm sure the previous owner would have complained and got the software updated. However, Audi dealer want to do this first to rule it out (which is fair enough as is a simple test).

The car is booked in again, hopefully the breakdown of the cable is visual enough for them to actually see the sender fault and change - I fear that as the tank will be empty for removal the fault might be hard to replicate.

Whereabouts are the senders located? Can a visual inspection be performed without dropping the tank?

[a8 tech]

Yes the sw update is very valid and i will add the fitment of the tank senders are critical in fact AUDI released a video of the correct installation methods because they are so awkward to fit correctly and simple things like the connecting fuel pipe from one side of the tank to the other can fowl the senders and only by filling can you confirm the sender floats are sat correctly,good luck to the dealer and i hope they resolve this and i would expect the senders will be replaced in this case.The tank senders are accessed from under the rear bench seat or luggage floor and you can remove them and test the end stop position whilst a multi meter is connected to measure the resistance from empty to full

[rharris]

Sounds like a bitch of a job; no wonder they were hoping the s/w update would do it!

:biglaugh:

At least the s/w update also got my bluetooth phone book exchange working, 3d sat nav mapping and graphical parking sensor display!

Thank you again a8 tech!

:beerchug:

[rharris]

Btw, under the boot carpet is an access panel with nothing behind it - so I guess that means looking under the rear bench seat?

What is the procedure for that?

Richard

[rharris]

Okay; the cover in the boot has no sender under it - neither does the cover behind the passenger under the rear seat - only the cover behind the driver under the rear set has any cabling and a sender present - is there another location to look for the other senders?

Richard

[Peter D]

There are two senders one either side of the partially split tank. Both are under covers under the rear seat but all the wiring goes through the drivers side fuel pump and sneder. PM me with youe email address and the year and model is this the new shape or older shape, for a drawing of the set up. Regards Peter

[rharris]

Its an 05 A6 (3.0 quattro s-line); i've had the rear bench seat out and only under the cover behind the driver is there a fuel sender and wiring; the other side just has a blank.

Richard

[rharris]

Okay; so 2nd trip to the garage to try and find the fuel gauge problem and they located a wiring problem (not covered by warranty; but being paid for by the supplying Audi dealer - which is not my local dealer).

Went in today to have the wiring installed and looking good so far....being an intermittent fault I'm not opening the whisky bottle just yet :)

[SpinneyA6]

Good to hear they've found the problem and nice that the supplying dealer is prepared to cover the costs.

I'm wondering if I've a similar problem with my car? I've a 2007 3.0 TDI and yeaterday the fuel gauge stopped working. I had about 3/4 of a tank of fuel, I parked the car, went to the shops and when I came back and restarted the engine, the fuel gauge read empty and the warning light and alarm sounded.

The cars going to the dealers tomorrow to have the condensation in the lights looked at so I'll get them to check this as well. I was wondering if there was anything specific I could mention to them to help them diagnose the problem?

Many thanks.

[proff999]

I had the same problem with 2005 A6 3.0TDI . Took it back to the dealer under warranty for replacement fuel sensor and got the car back two weeks later (Waiting for parts). Filled car with diesel, went to parents house and spewed diesel all over the drive. The fuel sensor had not be correctly seated allowing fuel to run out. Car went in again and came back perfect within 2 days.

Audi promptly refunded me for the cleaning of my parents drive and offered to pay for dinner with the Wife!

[rharris]

I was expecting it to be a sender change; but it does appears to be the wire that connects to the sender as so far so good....

As to given them hints, I'm sure they'll check the wiring - on mine they did a firmware update first to rule that out - and that's worth having - so let them go through their process... ;)

[SpinneyA6]

- on mine they did a firmware update first to rule that out - and that's worth having - so let them go through their process... ;)

That's the first thing they mentioned this morning. Hopefully getting the car back at 16:00 so I'll wait and see!