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battery drain - could it be linked to a central locking issue


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Okay so I've been having issues with my octavia vrs (2006) draining the battery. It seems to be a bit intermittent in that some times it take a few days to drain and other times it'll drain over night. The problem can be solved by removing the stereo/radio fuse (I've just been away for almost 3 weeks and without the fuse in the car started up straight away on my return, with the fuse is only just lasted a day or two). But given I'd had no trouble from the stereo for the first 10 months or so since I installed it I'm not ready to point the finger just yet.

 

I had heard of the can bus system not letting the stereo sleep if it's having problems from elsewhere, which might tally up with my experience today.

 

I parked up and locked the car using the fob, all doors locked by the rear drivers side door didnt, tried locking the car with key, still no joy, then I opened the rear door, put the child lock on and shut it, locked it with the fob and it locked (I doubt the child lock had any effect, more likely opening and closing the door did 'something'). Back home I had a bit of time to look into the symptoms based on what I've read on here and now I'm hoping someone might be able to offer some advice as it seems most people have a problem with the door not opening rather than not locking.

 

Symptoms are...

 

If I lock the car with all doors shut, then unlock it but don't open any doors it will as expected re -lock itself.

If do the above but open the rear passenger door, the car doesn't re-lock itself

If do the above but open the rear driver door (which wont lock) the car DOES re-lock itself.

 

Also

If listen to closely to the passenger rear door when I do the 'double unlock' on the key fob I can clearly hear two sounds that sound like the mechanism working, if I listen to the drivers rear door I hear the first of those but then just get a series of much fainter sounds (like the sound of a mechanism to being powered sufficiently to work.

 

Any ideas of where to look or what other test I could do to narrow things down?

 

Cheers

Gavin

Edited by DoctorT
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so after talking to the dealer it looks like the lock mech is at fault. So the next question, just from an interest point of view is, would a faulty door lock keep the canbus system active? (i'm curious to know if there's a link between this part failing and my battery drain issue which can be solved by pulling the radio fuse but didn't start until months after installing the new radio)

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Hey DoctorT,

I'm interested in seeing what's causing this problem in your car. Its strange that it resolves itself when you pull the radio fuse. Unfortunately I can offer no help, just an interested observer.

I just installed a 8" pumpkin HU in my 2011 Octavia and I'm really hoping that it's not going to cause the battery drain issue you have. By the way cheers for the great installation video you put up, it was a massive help.

I've seen a few threads about battery issues and the central locking. I wonder is the fact that the car hasn't locked up completely is the canbus seeing the car as still being active and failing to shut down fully? But what's the link to the radio I wonder?

Wish I could help but hopefully you'll find the answer. I really hope its not the radio as I'm loving the pumpkin head unit.

Cheers

Keith

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Hi Keith

 

Thanks for the response and I'm glad you found the video useful. I'm a huge fan of forums both for general interest and also because there's so much useful information on them, I figured making that guide was a good way to contribute. I have been meaning to post up a 'living with it and how does it perform' type video but like all good plans it's just be completed.

 

I would be surprised if its the stereo, purely because it's new and has worked fine for 8 months or so before this issue started. The only thing a could think, based on my very limited understanding of what I've read, is that if the can bus system doesn't sleep due to getting a signal from something then it keeps the car awake and part of that will keep the stereo awake, so what I wondered was, if the door issue keep the can bus system awake and that in turns keeps the stereo awake then that could explain what I'm seeing.

 

One symptom I saw that made me think of this was, if I switched the car off and took off the negative terminal from the battery and used my multimeter to complete the circuit I got a reading that was too high and would drain the battery in a day, now if I pull the fuse for the radio the draw falls away to what you'd expect from a car that is asleep/off. Now if I put the fuse back in, the draw comes back up, to me that suggests something is 'looking' for the radio and as soon as it's there, it wakes it up. If the radio was the source of the issue I'd expect it to stay asleep once the fuse has been pulled and replaced, unless I've overlooked something.

 

I've got the car booked into the dealers tomorrow for the lock to be investigated / fixed, I've also asked them if its possible to check the can bus software version too.

 

I'll let you know how I get on.

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Hopefully the dealer will find the problem and it will be a quick and cheap fix for you!!

It would be great to hear the outcome and if it turns out to be the radio then I can apply any fix thats needed. Yeah I agree these forums are a great source of info and help, would be lost without them.

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okay so the car went into the dealers today here in milton keynes and as expected the rear off side door lock was dead. I mentioned my battery drain issue to them so they could have that in mind as they looked at the door lock. They said that the door lock problem was leaving an open circuit and that would indeed drain the battery as the car wouldn't go into sleep mode with the open circuit. Which just leaves the question, with the radio fuse out does the car staying awake drain significantly less from the battery than with the radio fuse in?

Rather than try to answer everything i've just put the fuse back in now and i'll see if it starts in the morning. Some things just don't add up in my mind but i'm really hoping it was just an intermittent issue with the lock to start with which lead to my initial drain issues without the door staying unlocked (which i hadn't noticed before) and then finally when the lock failed completely it allowed me to identify the problem and that even in the 'awake' mode, with the radio fuse out the drain just isn't that bad. But i think i'm asking for the moon on a stick and fully expect my car to not start in the morning. Fingers crossed time.

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If your stereo is draining the battery it's usually down to the gateway control unit, pretty common issue with the earlier control units.

 

I'll drop the glovebox out and see what gateway i have in at the moment as a next step. It just seems odd to me that i've had the stereo installed since last summer, i had a flat battery some time in the winter before christmas, it was the first night the temperature dropped below freezing so i just assumed the battery was past it's best and the cold snap finished it off, i bought a new battery and all was well. Then the problem starts 4 months later.

The problem started shortly after i installed a hardwire for a speed camera detector, the first thing i did was remove the hardwire connection (i double checked and the fuse position I used was 100% an ignition switched live) and the problem persisted, i can only assume the problem starting at that time was coincidence.

The only other thing obvious I can think of is that, when I was installing the hardwire I put the car in my workshop where I also have a wifi router, typically I leave the wifi off on the stereo but if it was on at the time I wonder if the stereo did any sort of upgrade/update and something changed.

i'm just a little lost with the issue given the symptoms.

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okay so another twist, there are 2 relays in the fuse box under the bonnet that are the same part code and both seem to be responsible in some way for getting 12V power from the engine bay into the cabin as far as i understand. i replaced one of these with a new part and the problem continued, showing the same temporary fix, that if i removed the radio fuse, the battery drain stopped. Yesterday i swapped over the new relay with the other old one that i left in. This morning the car only just about started, and once 15 minutes down the road wouldn't restart at all even with the radio fuse still being out. Both yesterday and the day before the car had been used for good runs (around 25 miles each way each day) so the battery should be okay. Strange how swapping the relays has drained the battery overnight pretty much whereas without swapping them the car would last 3 weeks and still start without problem.

 

I'm charging the car at the moment and have swapped the original relay that's still in there with the other original one I took out when i put the new one in. Hopefully i'll get something positive from it.

 

Fingers crossed it's just a dead relay that'll cost just over a tenner or so.

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okay so I managed to get another new relay and have put that in the car. I've connected up my multimeter by disconnecting the negative terminal and completing the circuit with the meter. The bonnet is still open and I haven't fooled the car into thinking its shut, which might stop it entering sleep mode.

I see a spike of current up to around 8 amps when i unlock the car and holds at 0.84 amps if left sat unlocked, When I lock it, I see a spike to around 2.5 to 3 amps followed by a quick fall to 0.84 amps which over the next 3 minutes or so drops to 0.24 and finally onto a stable/steady fluctuation between 0.03 to 0.00. My understanding is that this means it's drawing 30mA which is less then the 40mA VW say is okay.

 

Does that sound right or can I not tell with the bonnet open. I'll check it again in a minute and then again 15 mins later to see what it's reading.

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so after 20 minutes or so sat locked but with the bonnet open i've see a draw fluctuating mostly between 0.00 to 0.01 amps with the ocassional spike to 0.02 amps, i watched for just over a minute and saw less than a few seconds worth of 0.02 amps being displayed (i have my multimeter set to the 10A scale/setting)

 

If any one has any experience of this i'd appreciate any imput.

 

Cheers

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Current readings look alright but remember that digital meters are subject to an accuracy of +/-  a % of full scale PLUS +/- one digit. So a typical 1% meter accuracy on a 10A scale gives an error of +/- 0.1A  and an additional plus or minus 0.01A. Check the spec for your meter.

 

But the main reason for comment is that I have found the hot weather has given me an additional current drain from the radio. The radio will come on by itself at a variable time after locking the car, sometimes in less than five minutes and sometimes it takes hours or not at all. Not noticed it turning itself off again, but it does occasionally switch from radio to SD card when it turns on. I suspect it may be because the can bus is running in single wire mode - but that fault has been there for some years with no consequence. Is your radio to can bus connection in single wire or two wire mode?

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hmmmm, i'm not sure about the can bus wire question. I made this video and at about 7.30 mins in you can see what i connected up. Does that tell us whether i did single or two wire mode

You would need to do a scan to see the fault of single wire operation. I used Carista. The single wire operation is not a fault in the radio but the connection to it

Radio

Part #: 1Z0035156M

Component: BOLERO

Coding: 0D0004000001 (hex)

[No fault codes]

CAN network gateway

Part #: 7N0907530M

Component: J533 Gateway

Coding: 352303 (hex)

Fault codes:

00470 Combination comfort Databus in Single Wire

An earlier scan said the faults were:

CAN network gateway:

01336 - Data Bus for Comfort System

00470 - Combination comfort Databus in Single Wire

00469 - Data bus Display / Infotainment in the single wire enterprise

I assume infotainment means radio.

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Ah okay, I had a VCDS scan done by Aston Bodger from this forum a few months ago when this battery drain issue began and it didn't show up any of those codes so i'm guessing i'm okay on that front.

I took the car off charge just before 7pm and checked the voltage at 7pm which read 12.54V. I'll check it again later tonight and see if it's heading down by the hour like it was before, hopefully not given the drain is hugely less than when I measured it the first time. It was originally 0.7 - 0.9A and now its 0.01 - 0.02A.

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well at 10.30pm it's reading 11.26V

 

I might have to disconnect the battery and check that it's not the battery that's dead, it's only 6 months old and it's a yuasa item but it has been put through the mill over the past couple of months as i try to narrow this issue down.

Edited by DoctorT
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just been out again, at 11.30pm its down to 10.88V

 

I put the multimeter between the -ve wire and the -ve terminal to complete the circuit and check the draw. Same deal as before, with ecar unlocked it drawing 0.8A but once locked, even with the bonnet up within a matter of 2 or so minutes, its down to reading 0.00 to 0.02 A which should be fine. Unless i'm missing something it looking like all of this has killed the battery. I guess the next step is to disconnect the battery from the car and see if it holds its charge then.

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A battery can be killed by repeated drops, a car battery does not like to be flattened as the plates start fail. If the battery is old, then Is suspect a new battery will be the order of the day as the current figures look ok.

 

At least its not my Audi that draws almost 15amps for 10 mins when you lock the car before it goes fully to sleep.

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well this morning at 10am it was down to just over 8V. I've spoken to my local halfords where i got the battery and they agreed it sounded like it needs replacing so i'll charge it up for a few hours then head over for them to test it. fingers crossed they replace it without issue and it solves my problems. It's such a pain having a car you can't rely on.

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So after charging the battery for a good 5 hours I took it to halfords yesterday and they tested the battery and agreed it needed replacing. Sadly my local store (less than 5 mins drive) didn't have the correct battery in stock. And no surprise the car wouldn't start again, so they called the next nearest store, told them they'd done the test and reserved a battery for me then jump started my car for me. The new battery appears to be okay, well things are looking good so far, yesterday evening the battery was showing a constant 12.65V and this morning at 9am it was still reading 12.45V. I'll check it a few ties during the day and see how things go.

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just to close this off (hopefully), the new battery has solved my problems, i guess judging by the high draw i saw when i connected the multimeter suggests one of the relays I replaced was dying as well, although i couldn't seem to repeat this by swapping the bad ones back in after putting the new ones in, but then i have heard of sticky relays that fire when you put them in or pull them out but then fail to switch in normal use so maybe it's that. Eitherway, £35 on a couple of relays and warranty change on the battery and the car appears to be behaving itself.

Edited by DoctorT
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