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packers1712

High current draw

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packers1712

Hello everyone,

 

I'm new to the forum and Polo ownership, well actually its my daughters car, the problem is that if the car is left parked for a week the battery goes flat enough to not start, I've checked the current draw at the battery which is too high, 0.1 amps, and narrowed it down to the circuit protected by fuse 30 which is for the "Onboard supply control unit".

Now I've read another thread on the internet that suggested a car with exactly the same symptom and the author wrote that the cause was that the control unit had been programmed for rain sensitive wipers and that he had cured it! I can't see that he mentioned exactly what cured it, my assumption is that the car was plugged into VCDS and reprogrammed or the unit was swapped for a different one.

Does this sound plausible and if so how do I go about finding out if my daughters car has the same problem without VCDS?

If not can anyone shed anymore light on the subject ?

 

Sorry forgot to mention its a 2003 1.2 petrol with 125000 miles under its belt!

 

Thanks in advance Doug.

Edited by packers1712
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Yeti

0.1A doesn't seem excessive to be fair. Have you checked that the battery is charging and holding a charge properly?

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Pete1

Maybe try unplugging connectors from the onboard supply control unit one by one until the current use disappears , or at least drops significantly? Don't disconnect the brown 6-way labelled XP2 though, that's where the feed from fuse 30 goes in.

The unit is above the accelerator pedal, with all the connectors facing the floor.

 

Once you've identified which connector the current is leaving the unit by, we might be able to figure out what's wrong (assuming it's not anything failed within the unit)?

 

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packers1712

Thanks Pete that's a starting point, I'll try that and report back. Have you ever known one of these units fail and is it possible to unplug said connectors in situ or does the unit need removed?

 

Thanks again, Doug.

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Pete1

Electronic units rarely fail within themselves in my experience, it's almost always something that's connected to them, whether that's wires with problems or motors/sensors/etc.

It's possible that the unit is 'staying awake' when it should be 'going to sleep' because of some other problem with a CAN connected module, but if you can prove one way or the other that the current draw is internal or external to the unit, that would be a fine start.  

 

I think though access is awkward, there is room to unplug individual connectors without removing the unit.

 

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packers1712

Good evening Pete,

 

Just been to check what we discussed in the earlier posts and discovered that when I disconnect plug XP4 my high current drops away! Any idea what plug XP4 controls?

 

Also found the thread that I mentioned in my first post its from this forum!

 

https://www.clubpolo.co.uk/forums/topic/266979-battery-drain-problem-9n-12-e-polo/

 

Thanks Doug

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Pete1

Hi Doug, I'll have a look, hang on.

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Pete1

Wipers seems to be the short answer. Although it does seem to also have other uses in some of the diagrams. It' a bit too late for me to focus.

How many wires do you have in that connector, all five?  What colours in which positions?

Does the car have rain sensing wipers?

 

Are you aware that according to this chart, the unregistered freeware version of VCDS should be enough to read the coding of this unit, and correct it if it has got corrupted?

http://wiki.ross-tech.com/wiki/index.php/Functions

So all you might need is a third-party cable to connect the car to a laptop.

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packers1712

Yes i have all five wires but no rain sensitive wipers - from left to right small brown/black tracer, large brown, orange/yellow tracer, white/black tracer and green/yellow tracer.

 

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packers1712

Here's a picture! The black plug.

XP4 connector.jpg

Edited by packers1712
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Pete1

Will have another look at the diagrams in the morning, but it does seem like it may be exactly the same issue as in the other thread. 

Oddly enough, a 9N3 Polo I saved from the scrappies recently has a current draw of similar size, which I've yet to investigate... It's off the road at the moment so I just disconnect the battery.

 

I wonder if @nige8021 has the coding info table for a 2003 Polo J519? I had a little look for one a couple of days ago but didn't track one down. Mine (2005 1.4) is coded 25758, but I'm not sure how that total is comprised.

Edited by Pete1
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nige8021
25 minutes ago, Pete1 said:

I wonder if @nige8021 has the coding info table for a 2003 Polo J519? I had a little look for one a couple of days ago but didn't track one down. Mine (2005 1.4) is coded 25758, but I'm not sure how that total is comprised.

There is nothing listed on the coding in Elsawin, as it just says "use the guided function on the VAS5051, so if you you have the full version of VCDS it should also give you a drop-down menu to guide you with the coding, if we weren't in lockdown I could pop over as Flitwick is only 15 miles from me 

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packers1712

Ok Pete thanks for all your help, the second paragraph of your last post all sounds a bit technical to me!

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packers1712

Thanks for your input Nige, I have a version of VCDS but its a "copy" from a few years ago and when I've used it on my wife's Beetle all I've been able to do is look at fault codes and some live data but never to run any tests.

 

Thanks Doug.

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Pete1
9 hours ago, nige8021 said:

There is nothing listed on the coding in Elsawin, as it just says "use the guided function on the VAS5051, so if you you have the full version of VCDS it should also give you a drop-down menu to guide you with the coding, if we weren't in lockdown I could pop over as Flitwick is only 15 miles from me 

Thanks for looking Nige, I only have Registered Lite, but I have a vague memory that it too may give dropdowns, so I'll have a play on the 9N3 later and see what I can find.

 

8 hours ago, packers1712 said:

Ok Pete thanks for all your help, the second paragraph of your last post all sounds a bit technical to me!

There are a number of configurable options in these controllers (e.g. rain sensitive wiper system/not, I guess), each has a specific 'bit' (0 or 1) in a byte of information that is the unit's 'coding' .  You arrive at the coding value by summing the decimal equivalents of all these bits (so 1s, 2s, 4s, 8s etc).  You just have to know which bit does what, and which options suit the car, then write it to the module. Sounds much harder than it  is. 

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Pete1

Doug; the thinner brown/black wire on pin 1 seems to be part of the interior light wiring.  The other four all seem to be front wiper-related.

 

Has anything been done to the interior light like LED bulb substitutions or suchlike, as far as you know?

 

Does the interior light come on as expected when driver's door is opened? 

 

Maybe try disconnecting the front interior light connector and reconnecting XP4, then see if the current draw is present/absent?

 

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packers1712

Good morning Pete, the one thing that does happen is that the interior light occasionally doesn't come on when the door is opened, I must admit I put it down to the latch assembly being on its last legs, similar to the one I have just replaced on my wife's Beetle! Just to add  that whenever I'm measuring current draw I do always latch the door as if it were shut so that the interior light is out, do you think that even if the light is out the there could still some how be a draw on the interior light circuit? 

 

I'll do the interior light disconnect this evening and report back with my findings.

 

Thanks again for ll your help.

 

Doug.

Edited by packers1712
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packers1712

Good evening Pete, I've tried what we discussed in the earlier thread and it made no difference to the current draw, so i decided to take the control unit out and open it and this is what I found.

 

I've just had a quick look on ebay for a replacement and when i searched the part number the one i found has come out of an Audi A4  diesel, could this suggest this is the wrong unit for the car?

 

The number on the front of it is 6Q1 937 049C.

 

Thanks Doug.

BCM.jpg

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Pete1

Ah, well done, that looks like a problem alright! Is that the pin which that thin brown/black wire goes to?  Now that I see your photo, I have a faint recollection of seeing damage like that before on one of these units, on another forum.

 

Any unit with an identical part number should be able to be coded appropriately for your car, but hold fire, I might have something in a drawer...

 

Do you have any scans of the car which might tell you the coding? If not could you try to scan that module (09 - central electrics) with it back in the car with the VCDS kit you have?

 

This is what you're looking for, and look, that scan (of my 9N) says I've got an intermittent issue with fuse 30! I don't remember seeing that before... 🤨

 

 

Screenshot 2020-04-24 19.24.54.png

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Yeti

A 6Q prefix is a pretty generic one on electrical components to indicate a part that is used on multiple vehicles. 

 

Probably worth chucking a new fuse in number 30, it might be a bit corroded or something. 

 

The contacts in the courtesy light switch can get a bit tired, so it's possible that's something to do with the intermittent fault on that channel. Try flipping it to off instead of door, clearing and rescanning, worst case, pull the courtesy light unit out and unplug it.

 

Klimaanlage is air con (where fitted).

 

I've got to be honest, I think you're performing brain surgery to cure a headache. I'd be happy with a drain of 0.1A on any car, particularly a modern-ish one like a 9n. I've checked the drain on my diesel Fabia and it's a hair over that, with no issues starting after a week. I'd still be thinking check the battery is getting charged right up. The steering is a huge consumer of electrical power, so if the car's just going to the shop and back, there's a fair chance that it's not getting fully charged. 

Edited by Yeti
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packers1712

That is actually on pin 1 of plug XP5 bizarrely! I'll have to wait until Monday before I can scan because the lead that i use to connect the laptop to the car is borrowed from a friend!

 

Looking at the code for your unit it looks as though it the same as mine so it probably is correct.

 

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Pete1
28 minutes ago, Yeti said:

I'd be happy with a drain of 0.1A on any car

100mA is about 80mA more than normal for this car, so there's something wrong, and the battery will discharge 5 times as fast as it should; why wouldn't you try to fix that?

30 minutes ago, packers1712 said:

That is actually on pin 1 of plug XP5 bizarrely! I'll have to wait until Monday before I can scan because the lead that i use to connect the laptop to the car is borrowed from a friend!

Yeah, I figured that by looking at a couple of other slightly newer units I have, though they are suffix-D at the end of the part number and lack that 14 pin IC just inboard a bit from the burnout.

I'll have to grab the one out of my 9N tomorrow and have a close look at it.

 

Interestingly, one of those two suffix-D units has a very dodgy/overheated looking solder joint at one end of the very same capacitor that has nuked itself in your photo.

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Pete1

Screenshot 2020-04-24 21.26.05.png

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nige8021

Looking at the picture with the exploded capacitor, some of the joints from the main connector to the PCB don't look that great either 

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