Parasitic Drain - Windows

Chat about your MKV (6N2) Polo
Post Reply
guye
New
Posts: 7
Joined: Sat Apr 11, 2020 7:09 am
Drives: 2000 6N2
Location: NZ

Parasitic Drain - Windows

Post by guye »

Hi, My daughter’s 2000 Polo 6N2 battery died. Put a new one in but it has a 52mA drain at rest across the -ve terminal, measured with a decent meter. Volkswagen docs recommend it be below 25. Pulled fuses and removing either #38 or #39 will reduce the draw by 18mA. Pull both and I’m down to 16mA. These fuse the circuits for the electric windows & electric mirrors. Disconnecting either door by unscrewing the bellows connector also drops the draw by 18 mA. Stripped the driver’s door pulling off connector blocks as I went. No change in the draw until the last one on the window motor was pulled resulting in an 18mA drop. Put it back on and current clamped each wire on the connector. Nothing, although admittedly I’m at the limit of the clamp down at this level.
So, slightly suspicious that both sides have the same draw. Both respond the same way to the bellows disconnection. Would expect some current flow through the window motor connector when its on, given it drops the draw by 18mA when it’s pulled off. Ideas, suggestions please.
Thanks, Guy
User avatar
937carrera
Silver Member
Posts: 430
Joined: Sat May 17, 2014 8:19 am
Drives: 2000 Polo GTi
Location: North Yorkshire

Re: Parasitic Drain - Windows

Post by 937carrera »

First of all welcome :)

I'll try and help, not least because I have a 6N2 with a battery that keeps going flat, so may have the same problem as you.

If I understand correctly, you have reconnected the door connectors and removed the switches one by one.

Be aware that the drivers switch also provides the feed to the switch in the passenger door, so once the drivers door switch is removed the passenger door one will not work.

If connecting the drivers switch causes a drain then I would suggest that is happening either in the drivers switch, or the passenger switch. What happens if the passenger switch is removed, that might narrow it down further

After that I would test the problem switch for continuity where there shouldn't be, and then either replace or dismantle / clean the existing switch. I suspect it's tracking through somewhere

Hope that helps
guye
New
Posts: 7
Joined: Sat Apr 11, 2020 7:09 am
Drives: 2000 6N2
Location: NZ

Re: Parasitic Drain - Windows

Post by guye »

Thanks for the reply, from almost as far away you could be. Where in North Yorkshire? We have a relative in Pateley Bridge.
I was expecting to get a result from disconnecting the window switch when I started on the driver's door, given what I've read about their common failure rate, but no. I got everything else on the door loom disconnected with no result before getting to the window motor connection. That's the one that makes a 18mA difference. Cant think why it would be drawing current. Not sure how to test further than this to definitively say it's a faulty window motor unit. I guess plug in another one and look at the meter, but I haven't bought a spare yet.
Also I'm suspicious that the passenger's side has exactly the same draw. I haven't stripped down the passenger door yet so don't know what's consuming the 18mA on that side. In the absence of a spare window motor I might crack into that for now. Should be much quicker than the drivers side now that I've got the process sorted.
User avatar
937carrera
Silver Member
Posts: 430
Joined: Sat May 17, 2014 8:19 am
Drives: 2000 Polo GTi
Location: North Yorkshire

Re: Parasitic Drain - Windows

Post by 937carrera »

Here's a wiring diagram in case you don't have one.

By all means swap the motors around to test, but I have two thoughts for you:

1. The motor is where the current draw is showing. It's possible this is just current tracking through poor insulation or a build up of dirt on the outside, maybe carbon on the inside ???
2. However that "short" can only occur if power is being provided. With ignition off there should be no feed to the window switches. Is it possible the tracking is further back in the circuit, at the fusebox / fuses for example

Not much I know, but maybe it will help in your though process

As for location - near Middlesbrough, so Pateley Bridge is South West for me
windows.jpg
guye
New
Posts: 7
Joined: Sat Apr 11, 2020 7:09 am
Drives: 2000 6N2
Location: NZ

Re: Parasitic Drain - Windows

Post by guye »

I pulled out the same diagram after the last posting and studied it along with the next page for tracks 43 to 56. Not sure if the ignition needs to be on for supply though it’s probably coming from a relay given the 2.5mm wire. The window motors would draw a bit when working. On the ground side the window control units go to two V69s (the key doesn't say what they are, will investigate further), and J393 which is the ‘Convenience system control module’. The connector I’ve been pulling off the window control unit J295 is probably the T18 which would stop current flow through the unit to the V69s and J393 (same thing if the bellows is disconnected). My theory now is that the fault is in one of these and that it’s pulling 18mA through each window control unit.
I’ve had a quick look for the J393 before. It's supposed to be above the drivers footwell. Couldn’t see it but will have a good look tomorrow and leave the passenger door alone for now.
User avatar
937carrera
Silver Member
Posts: 430
Joined: Sat May 17, 2014 8:19 am
Drives: 2000 Polo GTi
Location: North Yorkshire

Re: Parasitic Drain - Windows

Post by 937carrera »

Rather than pour over the wiring diagrams I just went out to the car.

Started it (because I wanted to make sure the battery had not drained). All good

Ignition key out, windows work

Locked myself in the car with the remote, windows work

It's looking like this is a battery live, unless the relay holds on for a period after ignition off
guye
New
Posts: 7
Joined: Sat Apr 11, 2020 7:09 am
Drives: 2000 6N2
Location: NZ

Re: Parasitic Drain - Windows

Post by guye »

Good thinking. That result makes sense. I guess you’d want to be able to open the windows from inside a locked car with the key out e.g. a kid accidentally locked in there.

I looked through the rest of my diagrams and V69 is the central locking pump in the boot. I tried pulling its connector off but that made no difference to the draw.

Also had a good look for the J393 convenience/comfort unit but couldn’t find it. Did some more research and found this very interesting post on another forum - https://www.clubpolo.co.uk/topic/328194 ... g-problem/. According to Christian6N in the reply it seems some basic Polos dont have J393 units and that the required ‘comfort’ smarts are in the window motor/control units. My car doesn’t have remote locking or an alarm so maybe it’s one of them. He also talks about the common connections between the windows and central locking as the open and close signal wires coming from the door locks. These are B133 and B134 on the diagrams. Pours water on the theory that the draw is to V69 or the (non-existent?) J393. Hmmm.

So, I’m back to the window motor units as the cause of the draw. Might strip the passenger door for the hell of it to confirm the other side. Looks like I might have to buy a good window motor/control unit to test with.
User avatar
937carrera
Silver Member
Posts: 430
Joined: Sat May 17, 2014 8:19 am
Drives: 2000 Polo GTi
Location: North Yorkshire

Re: Parasitic Drain - Windows

Post by 937carrera »

Pulling together / translating that post I observe the following

The J393 module is best thought of as the remote unlocking receiver. I did look for its location, but didn't find it either so said nothing.

The motor moves up / down either in the normal way through the operation of the switch, or by a one second press which moves the window down completely. The logic control for the one second press is built into the motor itself.

So, yes I agree, you are back to the motor units and testing for minor tracking.

If both motors are the same, then I would suggest that this is normal, and you're perhaps best just making sure that you have a decent main battery.

Maybe this will help:
063 battery should have a C20 capacity of ~40 AH (so 40 amps for 20 hours)
That measures from full charge, say 12.8v to 10.5v so 2.3 volt drop
800amps / 0.052 amps = 15385 hours
Assume you want to retain 12.2v in the car to start it (probably just enough), then that's 0.6 volt drop
15385 hours / 2.3 * 0.6 = 4013 hours, or 24 weeks

Mine is probably ok for about a week, but the battery has been discharged fully a few times so is way past its best, but absolutely fine if used regularly
guye
New
Posts: 7
Joined: Sat Apr 11, 2020 7:09 am
Drives: 2000 6N2
Location: NZ

Re: Parasitic Drain - Windows

Post by guye »

Now there’s a thought - this is normal. I might have been chasing a problem that doesn’t exist. Or if it’s not normal (more likely given VW say ‘no more than 25mA’) then it’s not significant enough to worry about with a new battery and regular outings. Hmmm.
Have you measured the drain on your Polo at rest?
User avatar
937carrera
Silver Member
Posts: 430
Joined: Sat May 17, 2014 8:19 am
Drives: 2000 Polo GTi
Location: North Yorkshire

Re: Parasitic Drain - Windows

Post by 937carrera »

So you're wanting me to go outside and start the diagnostics on my own car, something I haven't got round to for at least 6 months already :lol:

Obviously I haven't, but I would have done so right now if any of my 4 meters were with me at the moment.

I'll try and remember to bring them home with me later, hopefully I will have some readings for when you get up in the morning. Should provide a decent comparison.
guye
New
Posts: 7
Joined: Sat Apr 11, 2020 7:09 am
Drives: 2000 6N2
Location: NZ

Re: Parasitic Drain - Windows

Post by guye »

No, just thought you may know off the top of your head. We're in a mild autumn at 35 south not early Spring at 55 north. Keep off the permafrost, stay inside man, and no hurry.
User avatar
937carrera
Silver Member
Posts: 430
Joined: Sat May 17, 2014 8:19 am
Drives: 2000 Polo GTi
Location: North Yorkshire

Re: Parasitic Drain - Windows

Post by 937carrera »

Well, it's a lot colder this evening than it was this morning, down to 6 degrees C.

Came home and just done the test. After an initial peak up to over 1 amp, it then settled down to about 0.28 amps and after another minute dropped down again to a steady 35ma. This was done with the car unlocked, otherwise the alarm was going off, so alarm drain is additional.

Higher than the VW ideal spec, but lower than yours.

From my perspective I'm not seeing the loss of voltage in my battery as being due to a parasitic drain, so thanks for prompting me to do what I should have done months ago.
User avatar
937carrera
Silver Member
Posts: 430
Joined: Sat May 17, 2014 8:19 am
Drives: 2000 Polo GTi
Location: North Yorkshire

Re: Parasitic Drain - Windows

Post by 937carrera »

Just wondering how you got on with the second window regulator. Have you fixed it, or decided there is nothing to fix ?
guye
New
Posts: 7
Joined: Sat Apr 11, 2020 7:09 am
Drives: 2000 6N2
Location: NZ

Re: Parasitic Drain - Windows

Post by guye »

Hey man. Sorry about the hiatus. Life's been getting in the way. I couldn't get at the loom to window motor connector in the driver's door so I removed the whole regulator assembly. Then I pulled the window motor apart. It's the standard fixed magnet, brushed rotor, worm drive arrangement but with a fairly complex circuit board integrated into the case. I think this confirms what Christian6N said. You can only see the bottom of the board and would have to desolder 6-pins to lift it off and see the components on the other side. Photos attached. This is beyond my ken so I decided to stop at that point and put everything back together. Given that there's an even 18mA per side I suspect the draw is by design, but who knows. It's small enough to live with as long as the car gets a regular drive. I appreciate your interest and help with this. Thanks. On with the next project. Cheers.
Attachments
Polo 4.jpg
Polo 3.jpg
Polo 2.jpg
Polo 1.jpg
User avatar
937carrera
Silver Member
Posts: 430
Joined: Sat May 17, 2014 8:19 am
Drives: 2000 Polo GTi
Location: North Yorkshire

Re: Parasitic Drain - Windows

Post by 937carrera »

Thanks for posting back, and glad you have got to a conclusion on this.

Come back again next time you have a problem :)
Post Reply