A3 TDI electrical problem - conflicting dealer advice

[monster_munch]

I have a 2003 A3 2.0 TDI 140 with 53k miles.

Last week I had the car serviced at an Audi specialist, interim service with pollen and air filter change.
One of the report observations was that my battery test showed a loss of 153A, and they reccomended a bettery recondition or a new battery. They said the charge cycle worked fine so it was just the battery.

Yesterday on a long motorway drive, I noticed a bit of a notch in my steering, and it felt slightly heavier. Then about 10 minutes from home, the red battery light came on on the dash for about 30 seconds and went off when I pulled over.

I rang another garage this morning thinking it was going to be a new battery, and they were adamant that the red warning light was indicative of alternator failure.

I dont know how old the battery is in it now, I have had the car for 2 years and never changed it. The problem could be my fault, I have an in car hoover that I use at least once a week, Im a bit OCD about cleaning!

I am considering getting a battery from Halfords (I have a trade discount card) and fitting it myself.
Is it a straight forward job? I have retro fitted RNS-E and have the 4 digit security code. I presume I will have to re enter the code, but will anything else need changing or resetting when the battery is changed?

 

[Graham89]

Run the car up, get a multimeter and put across the battery. If its reading just over 14 volts whilst running then the alternator is fine. Turn car off then test again and check battery voltage, should be just over 12 volts i think.

 

[jsosic]

I dont know how old the battery is in it now, I have had the car for 2 years and never changed it. The problem could be my fault, I have an in car hoover that I use at least once a week, Im a bit OCD about cleaning!

Next time vacuum with engine on

 

[monster_munch]

Im afraid I dont have a multimeter.

Haha yes I wont be using the in car vacuum from now on!

 

[mike foster]

At that age, if it's an original battery, then it must be ready for replacement.

However, if you have been advised that the warning light was the alternator, then that should be the first point to test.

The car really needs scanning to identify the faults so that you know exactly what the problem is.

Check on VCDS user map for someone in your area who will be happy to help.

 

[chris.vincent3]

Go to Halfords and buy a multimeter with your trade card. As trying to guess which of the two it could be will be far more expensive than a useful piece of kit.

And by the sound of it, Audi tested your battery and the other garage took a guess over the phone. If I was you and taking a stab in the dark, I'd go for battery.

 

[NHN]

Varta Silver Ultra Dynamic battery if you must as thats very good, but yes also as said 03 car would ideally need new battery anyway regardless of alternator state.

 

[WilkyA3]

From my knowledge the battery light on the dash indicates wheter the alternator is charging?

 

[chris.vincent3]

From my knowledge the battery light on the dash indicates wheter the alternator is charging?

Nope, indicates if there is a charging fault, if it be the alternator not charging the battery by being faulty or just simply not being driven by the belt or the battery not holding a charge as well as loose terminals or even weak earthing points.

 

[WilkyA3]

So how does it do that then?

 

[chris.vincent3]

So how does it do that then?

Weird feeling its a sarcastic question. But, a live wire from the ignition switch to the battery warning light which is connected to the alternator (which is fed from the battery) when you switch on the ignition, you get a live to the warning light bulb, and the alternator which isn't rotating acts as an earth, so the bulb lights up.

Once the engine is turned on the alternator starts to rotate creating an electrical source which in turn cancels out the 12v from the ignition because its getting 12v from both sides and no earth, which causes it to turn off, only way it will turn back on again is if one of those two 12v feeds are removed, which is more than likely from the charging circuit.

Its a very old system and wouldn't surprise me if Audi do it a different way so don't hold me on this.

 

[WilkyA3]

So the light does indicate wheter the alternator is charging or not? I was just pointing out that nobody had mentioned the fact of the light on the dash. I've seen faulty alternators be the demise of the battery. Lots of people fitting new batteries then a few month down the line your in the same boat as the batteries been taking a hammering.

 

[chris.vincent3]

So the light does indicate wheter the alternator is charging or not? I was just pointing out that nobody had mentioned the fact of the light on the dash. I've seen faulty alternators be the demise of the battery. Lots of people fitting new batteries then a few month down the line your in the same boat as the batteries been taking a hammering.

That is one cause of the light staying on yes, but unless its been tested, eg with a voltmeter, there is no point in guessing, process of elimination in an expensive way to fix any vehicle.

The warning light had been mentioned, but as i said, doesn't necessarily mean it is an alternator fault, because say if it was the battery at fault, the alternator would be able to supply a voltage to the battery constantly maintaining the 12v needed, which will keep the light turned off, however over working the alternator because the battery can not hold the charge in turn killing the alternator as well eventually.

I can only give advice. Unless you test your situation anyone could be right or wrong.

 

[monster_munch]

Thanks for all the helpful replies, especially chris vincent.

As the garage who serviced my car checked the connections with a multimeter, said the charging cycle was fine and reccomended a battery recondition, I have just bought a new battery today.

I bought a Bosch 12v silver car battery from Halfords with 5 year gurantee. It should have been £117 but I got it for £92 with my trade discount card. Halfords | Bosch 12V Silver Car Battery HSB096

Provided my car gets me home tonight, I will fit it tomorrow in my lunch break and hopefully it solves the problems. And no more car hoovering unless its using external power!

 

[WilkyA3]

Without being argumentative your contradicting yourself you originally said "only way it (the warning light) will turn back on again is if one of those two 12v feeds are removed" Now your saying the light would stay on if the battery was at fault.

When the alternator is charging (engine running) if for some reason the battery voltage reduced (in comparison to the alternator) the light would come on, and vice versa.

 

[chris.vincent3]

Without being argumentative your contradicting yourself you originally said "only way it (the warning light) will turn back on again is if one of those two 12v feeds are removed" Now your saying the light would stay on if the battery was at fault.

When the alternator is charging (engine running) if for some reason the battery voltage reduced (in comparison to the alternator) the light would come on, and vice versa.

Yes because there would be a voltage from the alternator. And to your other question no it wouldn't as the alternator is putting out a charge, but say if there was 3 voltage supplies one from the ignition barrel, alternator and the battery then if one did fail then yes it would illuminate the bulb because that live wire would then be an earth in turn completing the circuit. Any more questions?

As for the battery you've bought that's the same one Ive got in mine, a very good battery. Just keep the receipt for 5 years!