My 2002 A4 Quattro 1.8T has its original battery.

Today I accidentally left a thermoelectric cooler plugged in after I turned off the engine. It is nominally a 4.5 Ampere drain. A little over two hours later I heard beeps like the intrusion alarm, and found the car only partially responsive to door lock/unlock from the fob. Noting the dim dome light, I turned off everything and waited a half hour before attempting a start. The engine turned perhaps once. So I put on a charger for a few hours, then started the car and checked for effects.

1. the clock forgot date/time--easily fixed
2. the trip computer forgot data--no problem
3. the alarm beep for low fuel quantity sounded immediately after start, with the pump symbol on the dash. The gauge reads below the lowest tick, and the remaining miles before empty field in the trip computer reads zero.

This last has persisted through three start/stop cycles, including two five mile drives. As I filled the tank less than 50 miles ago, I believe it has about 15 gallons in it.

As the battery is stamped with an 80 Ahr rating, I think I just got a cheap warning that I need to shop for a battery soon, certainly before cold weather.

The gasoline gauge thing puzzles and alarms me. I own a code reader (ScanguageII) but it does not return any fault codes.

Any ideas?

 

I think it will come back on its own in a while. I have noticed such a behavior in mine.

 

My gas gauge did the same thing and it went back to normal after a 15 minute drive. But, this was after I replaced a drained battery.

 

Did it change in the middle of the drive to working correctly? Gradually or suddenly? Or was it wrong throughout the 15 Minute Drive and then correct the next time you started it?

So far mine has stayed firmly at zero through four drives of about seven to 10 minutes each.

 

Over the course of the drive, the gauge slowly went back to it's normal reading. By the end of the drive everything was back to normal.

 

By this afternoon I had driven the A4 six or more segments since the event, totaling a hundred miles. The last segment before I refilled gasoline included over a half hour of 70 mph freeway driving. Throughout the needle never budged from a position well below the lowest red tick, and the "miles until empty" display in the trip computers stayed at zero.

I never normally put in gasoline past the first click, but this time I nudged it a bit, as I fancied my last best hope was that something in the car would notice the filling, and bump whatever computer was in a bad state into one in which it was willing to notice the float signal. I was able to get 3.36 gals in (just the amount my ScanGaugeII thought I'd consumed since last fillup).

On starting the car, the gasoline needle gauge promptly rose off the bottom, initially settling a little below the quarter tank tick. Miles to go initially read 80. As I road uphill at 20 mph the mile to home, averaging about 20 mpg, well below recent average, the gas gauge rose to just barely above a quarter, and the miles to go moved up in several increments to 105.

I assume I am now started on the roughly 15 minutes of driving required for it to get close to the truth.

In my state--possibly because of the relative full tank, possibly because my computer was down a different detour than the two folks posting above--it seems that adding gasoline was key. I don't know whether the problem would have persisted through the consumption of 14 gallons, nor do I know what minimum addition of fuel was needed to bump things into progress.

Thanks to those who posted, I've added this much detail in hopes that perhaps someone in the future with a related problem will come across this thread and learn something from it.

 

Exactly the same thing happenned to me. It was just a matter of time.

 

did everything else on the dash work? I have a 98.5 A4 and my whole dash went out - the speedometer, tach, gas, and oil temp are all at 0. Did this happen to you as well or only the gas gauge?
Thanks

 

Speedometer, tach, and water temperature all operated completely normally from the very beginning of my episode.

An update: I drove the car another twenty-two minutes today. With a total of about 25 minutes (and 10 miles) since the fillup that seems to have triggered the beginning of return to normal the miles remaining indicator has just now reached apparently normal level. The panel gas gauge is still reading about a needle-width below the level I'd expect for the current state of the gas tank. The recovery was entirely gradual, with both the remaining miles and the needle position moving steadily toward normal throughout the 25 minutes of driving so far.

I'll speculate that the recovery time if you do a full fillup may be related to how much gasoline was actually in the tank at the time--as it appears to initially display just the added gas, and slowing "realize" there is more. Perhaps had I filled a tank with much less gas in it the recovery period would have been less--looks like about 30 minutes driving time in my case. And I think it is time, not mileage. I actually saw the gauge and the miles to go both move up while I sat waiting at a stop light.

 

The stealership had my car (with a full tank) for 3 weeks for tranny work. I got in with a dead battery and it did the same thing to me. I went to "fill up", swearing at them for wasting $75 worth of gas, and charging me to "put in enough to test drive it". It took about a week and a half of driving to empty the tank, put in a full tank, and have it play catch up. It was instant though, probably because I drove it to "E" and then filled up. Stupid stealership... Never heard of a battery trickle charger?!?