Battery drain problem

[johnmac]

Car is 2001 Arosa. Can anyone please suggest a possible cause for battery drain exceeding 1.0 amp when car is locked and everything is switched off? Until three weeks ago there has never been a problem, but this is now consistent and the battery is flat in a day or two. I have substituted a new battery, and removed the radio & CD player fuses, with no change. The batteries old & new are both fine, and hold a charge when the earth lead is disconnected, but something is taking quite a current. Local garage monitored and said all OK. But two days later the battery was flat again and I checked -- the drain current put my 1 amp meter off the scale.

 

[Simon Audi]

Hi,

No real suggestions as to the cause, could be one of many things. Pull the interior light bulb and then pull all the fuses from the fuse box, connect up your meter to measure the current and start putting the fuses back until you find the one thats causing the draw, that will give you the circuit to look at.

Sorry I can not be more helpful.

Simon

 

[johnmac]

Thanks, Simon. I'm reassured by your suggestion. I was going to go the other way round -- pull the fuses one by one until I found the bad one. However, a guy at the garage said pulling some fuses could foul up the airbag or engine management circuits -- any views on that?
John

 

[Simon Audi]

I would not expect any issues with this, but I am not an Auto Electrician, I am a Mechanical Engineer (but I have done lots of electrical trouble shooting on million pound automated machines).

Pulling the fuse, effectively disconnects the power to the circuits, the same as disconnecting the battery, or turning off the switch. As far as I am aware the only issue that can arrise from disconnecting the fuses or battery is a security code problem with your stereo, and in some cases, your Engine ECU etc to reset to factory settings when its reconnected, which is no big issue.

As long as you do not short anything out, and replace the fuses with the correct value in the correct place (take a photo to make things easier) then I think things should be fine.

Make sure your amp meter is connected securely and in the correct polarity between the battery terminal and lead.

Regards

Simon

 

[cupra_matt]

Battery drains are a problem, i hate getting them at work and mercs suffer a lot. My method is to lift the bonnet boot open all doors so you have access to the interior, then close all the latches on doors and bonnet and lock the car.

Monitor you battery drain and begin methodically to remove one fuse at a time. Eventually you will find the fuse causing the drain. So now you know what circuit your dealing with, and normally the consumer is at fault, but there maybe more than one consumer on that circuit so be careful.

The most common things i find that caused battery drains on VAG vehicles were radio's / sat nav and instrument clusters.

When your car is (right) expect a drain of around 0.06 A no more than this really. This is what audi say is acceptable.

This is my method and not necassarily the correct method, and dont worry about talking fuses out, as your ignition is off so you shouldn't get any warning lights.

Hope this helps.

Matt

 

[johnmac]

Dear Simon Audi and cupra_matt
Thanks very much for your advice, and very quick responses. Sounds like I've got a busy day ahead! I'll let you know what I find.
johnmac

 

[s10mph]

If you have tried all the above and the problem persists then I would be suspecting the alternator. as well as be being your charging device it can also drain the battery. You really need an ammeter to fault this yourself.

 

[johnmac]

Thank you s10mph. I'll let you know what I find.
johnmac

 

[johnmac]

To Simon Audi, cupra matt and s10mph who gave advice.
I've now checked all the fuses, including the four in the battery +ve terminal box. Current of more than 0.1A (according to my meter) is flowing in six circuits: instrument cluster, engine, 2 x powered window, alarm and radio. Problem is when I pull all those fuses I still get something > 1 amp flowing out of the battery. I can't check the alternator as I can't get at it. Presumably it has some rectifier and regulator circuitry. Could a diode have shorted? Does the alternator charge feed into the cable on the +ve battery post?

 

[Simon Audi]

Hi,

If I read your reply correctly, with all the fuses pulled you still have excess drain >0.1 Amps?

There should be 3 leads coming from the battery positive, 1 on the main terminal, the other 2 from the box on the top.

Does your ameter only register to 0.1 amps?, if so buy another one before you go much further.

Disconnect the two leads from the box on top, leaving only the 1 main lead connected to the terminal.

Pull the terminal from the battery, and measure the draw using the ameter, assuming negligable current, with the ameter still connected, touch each of the other leads in turn to see which one is drawing the power.

I believe, (but am not sure) one of the leads goes to the fuse box, one to the alternator and the other the starter motor. It is possible the alternator or starter motor has a short causing the problem, by testing this way at least you can identify which of the 3 supply leads is causing the fault, and this should then limit your search.

Sorry I can not be of more help.

Ciao

Simon

 

[johnmac]

Hi Simon

My meter will measure up to 1 amp, and I may have to get another.

However, I did check each lead in turn and eliminated the red and black leads going to the the battery terminal box. This led me to the fuse box where I identified the ones I listed as "hot". I don't have a circuit diagram, but couldn't imagine why any of those circuits except possibly the radio (on standby?) or the alarm, should draw current when not in use.

I'll go back over everything, and maybe buy a new ammeter before I start!

Thanks again

John

 

[traumapat]

sounds like youve eliminated this already but i had similar issues which turned out to be the courtesy light in the boot.

good luck finding your issue

 

[Simon Audi]

Hi,

If you have disconnected the two leads from the box on top of the battery and they were good, then I would expect (but am not 100% sure) the alternator and starter motor can be ruled out.

Go back to the 5 circuits you previously mentioned, and measure the actual value with an ameter.

I do not know why the Instrument Cluster should draw power with the ignition off, other than possibly a small feed to keep the memory up.

As for the Engine, I am not sure whats pulling power there either with the ignition off, unless the fuel pump is constantly running, or the coils powered up?

The 2 power windows again will have power to the switches and motor, possibly with the ignition on and off, but should be minimal - like no power consumption, if this is higher reading than the rest, then maybe you have water in a motor or switch or connector causing the problem.

The alarm also will have power, but again should be next to nothing.

The radio too should have power, but again next to nothing unless its on.

Post the measured current values and perhaps that will give a clue?

I am not sure if the car has a convenience module that may be a common feature in all these circuits? if so that could be the problem??

Sorry I can not be more help.

Simon

 

[johnmac]

Hi Simon
Thank you for detailed guidance. I'm out of action for the moment until I get a decent ammeter and get the car back - (it's my daughter's).

I'll get back to you with more precise info as soon as I can.

Thank you for all your help. I'm beginning to feel I could become a drag on your valuable time!
John

 

[s10mph]

Simon audi's advice is quite detailed, I can offer no more than him now. You are right saying diodes in the alternator can break down.

 

[Simon Audi]

No worries!!

 

[cupra_matt]

Do me a quick favour, With the engine running, set your volt meter to volts, and put 1 terminal on battery negative on 1 on engine itself on a metal part such as a bracket etc, tell me the reading you get.

Thanks.

 

[Simon Audi]

Matt,

You have me curious, what are you looking to see and why? - Should be 0V as both are earth, or are you thinking a bad battery earth??

Thanks

Simon

 

[cupra_matt]

This will show an earth problem between engine and battery earth. The reading will never be 0V but as near as, anything over 0.3V and there is a problem. I had a car in yesterday with a reading just under 4 volts, which turned out the main earth lead between gearbox and chassis was loose, this was in for a battery drain problem.

The same can be done with a feed line. the consumer has to be switched on. Positive on power source and negative just before the consumer, if a reading more than 0.5V is read then there is a problem on that line.

When testing a vehicles wiring a Volt meter is all you need. This all comes from my extensive Audi electrics training. Hope it is of some help.

 

[Simon Audi]

Matt

Thanks - Always keen to learn.

As you are an Audi guy, wheres the OBD 11 port on the A3 - 2007?

Thanks

Simon