Low battery problem

[ml82]

I'm new here so hello everyone

My problem is that the alternator (or something around it) does not charge the battery, most important it happened after service I've done like 2 weeks ago. Now I'd like to discover the problem as much as possible before I go to garage and they'll eventually quote me for hundreds. Please help if you can! I also searched this forum but couldn't find any /direct/ answer to my car's problem(s).

Quick intro about car:
I bought 2003 A3 2.0 TDI from some amateur car dealer. Battery was flat (he said because the car wasn't used on daily basis), so we jumped battery, did a test drive and I decided to buy it (somewhat cheap) despite some issues with the car. Also the ESP light was on all time, but I thought it might be only due to fact of previous flat battery. Then I was driving it for 2 months (=5k miles) and everything was okay (apart from the ESP light on).

I had service due to so I went to do it (at independent Audi/VW specialists). There's no big issues with the car at all. I asked for resetting the ESP. It was reset and I was told if it pop ups again then it's one of the Brake Pressure/Steering angle/Lateral Accelerator sensors, or faulty ABS pump or steering wheel. After the service I managed to drive around 100 miles till the battery drained out completely. I was lucky enough I wasn't going fast (the car basically died in 3-5 seconds). I bought new battery (ESP was back on). I investigated a bit and discovered the engine dies when I disconnect the battery (so potentially alternator doesn't work). But then I started moving the wiring cable which goes to alternator and the engine was running more "smoothly". I drove another 200 miles last week, then left the car parked at the airport as I went abroad for few days. I was driving home last night when the battery drained out on M1 (yup, a bit not funny!). I ended up calling AA. This was brand new battery, fully charged. I didn't use any extra electric equipment (radio, satnav etc) in the car.

There's also issue that I can't see battery light on the dashboard while starting up the engine. I hope it's only faulty bulb.

So guys what do you think the issue here is? Let's forget the ESP light for now (or maybe not . After the service there's something which gets the "juice" away from car's battery. I was quoted 250 for new alternator (but I reckon it was already changed at some point), but when I provided more info the mechanic looked a bit confused about the problem and said it could be something else which they need to investigate of. Anyway, I've got appointment on tomorrow. I'd love to know what the trouble is before I get quoted for something expensive while it could be something simple and cheap to fix.

I'll be thankful for any advices.

Matt

 

[Chillout]

Do you know your battery voltage when running and under load sounds like have bad connections earth strap or associated

 

[ml82]

When alt is working around 14V if not around 12V

 

[ex911driver]

Get it scanned with VCDS to try and pinpoint problem

 

[ml82]

Well, I got it scanned at garage, that what they say:
"Labour to diagnose and re set 3 separate faults on ESP

Brake Pressure Sensor
Steering angle sensor
Lateral accelerator sensor

All faults due to either the ABS pump renewed or steering wheel taken off for previous work. No guarantee given for further resetting and if ESP lights return then further work is needed."

After the service something started drain out the battery.

 

[Geraldy212]

Silly question, but have you looked closely at the glove compartment interior light? Common problem on the A3 when the glove compartment door mechanism fails (door drops down quickly) and the damn light stays on forever. Well known for draining batteries.

 

[ml82]

No this is not silly question But the glove compartment light does not work at all LOL. But that won't be the problem, as it started draining battery *after* I did service on this car (as they reset some functions on computer probably).

 

[MrLapou]

Easy enough to check. Take the bulb out of the glove box compartment.

 

[Geraldy212]

Mr. Lapou is right, take the bulb out. Who knows someone may have fitted a crap LED bulb and the resistor is pulling current. You can check this by touching the bulb holder and see if it is warm. Same goes for the boot illumination. Otherwise, get an electrician to put an ammeter in-line with the + terminal to see what current is being drawn. I am sure a forum member can tell us aprox what current to expect with the ignition off. Whatever it is, it should be very small.

 

[NHN]

Find a decent garage that knows what they're talking about, seems you have dealt with people with not allot of experience in audi's by your info, ideally all wiring needs checking for alternator & associated parts, get a professional to look at it as its already been several months, also I do wonder if someone's put some tape over the battery led in cluster to mask the fault.

 

[percymon]

When alt is working around 14V if not around 12V

with the engine running you should see ca 14.1-14.4V when you measure the voltage across the battery connections.

With the engine stopped i'd expect to see 12.5V just after the engine stops, dropping to ~11.8V after 5-10 minutes and stabilising at this. If after an hour or overnight its dropped below 11.0V then you either have a current drain from somewhere (tracking device ?, bulb etc etc) or the battery has a defective cell. The fact the car started after a prolonged period at the airport is a bit strange, for it then to fail once the car is running. Maybe a defective diode pack on the alternator ?

You say you bought a new battery - is it the correct rating ? (size and Ah rating). Has the new battery been load tested ? (tyre / battery places will do this free of charge normally)

Your faults for all three sensors are all related to the ESP system and this always throws faults with low voltage conditions - don't spend money replacing these until you have resolved the voltage issues.