Parasitic battery drain

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Philmk6
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Parasitic battery drain

Post by Philmk6 »

Hello . I have a 2008 (58) polo tdi. I am experiencing problems with the battery going flat after about 2 or 3 days. I have checked out the battery drain and it's 124 milliamps when it's all locked up. This is pretty high so I did the check with the fuses by removing them one by one and found that fuse 5 was the culprit which is one of the engine management fuses.

If I switch on the ignition with this fuse removed the power steering warning light and the
Battery light dont come on but the car runs ok. Is it possible that I have faulty diodes in the alternator which is causing the drain?.
The alternator gives out 14.4 volts when running
Any ideas out there?
Thanks in anticipation. .
RUM4MO
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Re: Parasitic battery drain

Post by RUM4MO »

You can check the alternator output lead for leakage/drain by just removing it from the fusebox/distribution end. I did lots and lots of checks on a late 2009 SEAT Ibiza 1.4 16V SC, to do that I made up a monitoring lead that I connected across the battery terminals and fed out to the front of the car - logged battery voltage daily so that I could work out if it was being drained all the time.

Now, you do know that all "not required" controllers are being put to sleep after maybe 20 minutes from ignition off, so if measuring drain within that period you will get a much higher than normal drain, on later cars maybe even 250 milli amps, when all systems are asleep it should drop to maybe less than 50 micro amps. Any removing/fitting of fuses will probably awaken some if not all systems which is why the official way to check for drains is to measure the voltage drop across each of the fuses, that is the VAG method of doing things it seems.

In my case, there was a known issue with the coding of the controller that controls the power supplies, SEAT locally were not aware as it was, by that time, a 8 year old issue and most cars had been brought back in with this issue, so that lead to me needing to spend money at the first SEAT main dealer getting them to investigate and claim to have found a fault with the steering angle position sensor which was only used on that Ibiza to switch on the front fog lights to act as "slow speed turning lights" - you told the dealer that I didn't think that that expensive component was the root cause - but they knew better - then before I could demand that they check with SEAT UK about this known drain issue, they closed down! So I went to my next nearest SEAT dealer service desk and they had just had a VW Polo traded in with the same problem and got it resolved by talking to VW, so they were willing to check this car and if nothing was found faulty, submit a request to SEAT UK for tech help, that resulted in them being informed about an available S/W patch which they down loaded and sent up into the that car - problem solved, it only took me about 18 months!!

So, if you have exhausted all your checks for faulty wiring or components, then hand it into a VW dealer to get a battery drain investigation carried out, this will take maybe 2 or 3 days but the charge should only be 1 hour at techs rate, if this comes back inconclusive, request that they contact VW UK for technical support as maybe some late 9N3 Polos had this same issue as the early 6J Ibizas.

I can't explain why a car that was 8 years old only started to show that issue then, maybe change of use pattern and/or battery aging - it certainly had a change of use as I was looking after it while my daughter was away working abroad - but initially it seemed to last okay with only being used at most once a week.

Good Luck!

Edit:- by the way, I did try removing groups of fuses then refitting some, sometimes there was a repeatable change and that change seemed to remain for some days, though mainly it was just a quick change that when repeated 10 times showed no consistency - which was really annoying, I did not need that car so it was easier for me to check and log lots of changes/events. After it was worked on by the first SEAT dealer and given a clean bill of health from any battery draining issues, we used it to go on holiday, left it at the local airport for 7 days, but played smart by putting a battery pack in the boot, returned from holiday - engine turned over and failed to start, then next time was dead, got it running using the spare battery pack - but that did prove that very little had changed after having work and a component replaced!! After that I bought a CTEK battery tester and it proved that the battery was past its best, I replaced that battery with exactly the same new one, all that did was to extend the point at which the car could be left normally to 7 days, but some times only 3 days, so not a fix.

Another Edit:- does the charge fail light always come on when you turn on the ignition, if not check the leads under the gearbox, ie the load sense wiring and the alternator initial excitation wiring as it seems that these alternators will, when the engine revs are raised, start to self excite but if left idling will not so the charging voltage will stay low until reved up to over 2K RPM.
Philmk6
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Re: Parasitic battery drain

Post by Philmk6 »

Thanks for the info RUM4MO, I will consider all options and update the thread accordingly
Cheers 😉
PugBrothers
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Re: Parasitic battery drain

Post by PugBrothers »

Philmk6 wrote:Thanks for the info RUM4MO, I will consider all options and update the thread accordingly
Cheers [emoji6]
Hi Phil! Did you ever get to the bottom of this problem and find a solution? I’m experiencing an almost identical issue and short of buying a new battery I’m completely stumped!


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Philmk6
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Drives: Mk7 tdi facelift
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Re: Parasitic battery drain

Post by Philmk6 »

Hi PugBrothers. Sorry for the big gap in responding but as you probably can imagine its been a crap year. I came to the conclusion that the problem was being caused by a dodgy diode in the alternator. I have continued to live with the problem since and did not bother getting it sorted, as long as i dont park iup for more than 3 to 4 days is ok and will start. Did you get yours sorted?
Cheers
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