I've got a battery drain, but no apparent electrical problems?

[pants1984]

Hi,

I'm hoping somebody could help with an electrical drain i've got on my MK1 Octavia VRS.

When my car is locked there's a draw of 210mA which is killing the battery in two or three days. I've left it locked for at least 20 mins and the same draw is still there even after all of the systems should have shut down:

I've isolated it to this wire. When it's pulled there is no current being drawn:

That's not too helpful because I have no idea how much stuff this wire powers. So to try and narrow it down some more i've tested the individual fuses in the fuse box at the drivers door:

In that picture i've taken Fuse 14 out (3rd in, 3rd down, from the top left) as this is the only one that seems to change the current draw. When that fuse is pulled I am getting a much more respectable 50mA total draw from the battery - although even that seems a little high:

I know this fuse is interior lights (of which none are switched on), but i'm not clear on what else it's doing. To dig a little deeper I tested the current for just this fuse. This is where i'm getting really confused. This fuse only draws a small 20mA. Although the total effect on the draw from the battery is 160mA:

So i'm a bit lost on what to do next, and this is annoying the hell out of me. If this fuse box isn't using the power then what the chuff is? Am I being daft and missing another fuse box or something?

Appreciate any help!

Cheers.

Anthony.

Edited 27 March, 2012 by pants1984

[Raf_]

Have you checked to see its not the boot light?

[nitrovrs]

as above, boot light and also fan control relay (under battery) are known issues.

[rwbaldwin]

Have you checked to see its not the boot light?

+1

Some central locking problems can also cause this problem. Does the LED flash when the doors are locked (deadlocked)?

[pants1984]

Hi,

I've checked all of the lights, and the fans are all off.

The door led flashes when I lock the car with a single click (a double click stops the flashing), and all other electrics work properly too.

The only thing that came to mind is that my rear wiper motor seized up ages ago. I thought that could have caused the drain, so I removed the plug. It didn't change anything.

But I wonder if the Central Convenience Unit would not shut down if it could somehow detect the rear wiper motor is disconnected or not in the parked position? I have no idea.

I think the next step if for me to check the drivers door plugs and keep trying to find the drain. Could anyone tell me where any other fuse boxes are as the drain isn't in main one by the drivers door.

Cheers

Anthony.

[mannyo]

Glovebox light is another common one and harder to check since it only switches off when its closed.

There are a lot of relays in the drivers footwell if you remove the lower dash panel.

[pants1984]

Just checked the plug in the drivers door. All looks OK: (followed the first part of this great guide http://www.briskoda....ch-microswitch/ )

Also pulling this plug out takes the total consumption from 180mA to 140mA:

Damn, I was hoping it would be this plug so I could just WD40 it! More searching.

Edited 31 March, 2012 by pants1984

[pants1984]

After more interior removal I've got to the Central Convenience Unit (I think).

When I take the centre-most plug out of this the draw from the battery drops right down to 10mA. Sweet.

The next thing is, how do I work out if this control unit is faulty, or if it's something connected to it?

[Lew_VRS]

Could you not borrow a spare one someone may have (or buy one and see)? If it still drains take it back and get a wiring diagram.. chase the pin outs and see where it leads

[pants1984]

Just bought a used CCU from the ebay http://www.ebay.co.uk/itm/170816451299. So I'll see how that goes in a few days. Just ran a fault diagnostic on the unit in VCDS Lite and I'm getting this:

Not very helpful because I don't know if there are really no faults or if it's a DTC / comm error. Sigh.

On an unrelated note my car failed it's MOT due to a leaky Weitec rear damper that was fitted under a year ago. I think this one had a manufacturing defect:

Bad times. :(

Edited 1 April, 2012 by pants1984

[Sampolainen]

I was just about to tackle a similar drain. I'll be following this closely.

[chicken_eyebrow]

I don't think you can read CCU errors with VAG-Com like you can fault codes on the ECU. There's no CAN-bus output to the diagnostics port from the CCU.

Thats a bit worrying about the Weitec damper, lot of people on here with those fitted (my old car included)

[pants1984]

The new CCU did the trick I think. Battery should last ages now, Just Like A Golf.

One slightly fail thing I've done is not got an exact replacement, because my key fob no longer works. I think there might be some other curious behaviour too like the indicators flashing for a good 10 seconds after I've unlocked the car.

I need to try and find out if/how I can recode this CCU and copy over my Skoda settings...

Edited 3 April, 2012 by pants1984

[Raf_]

You're right there CCU will need coding to the car

[pants1984]

Is there a guide anywhere to show how you copy the settings from one CCU to another with VCDS?

I've done a search but can't find anything.

[chicken_eyebrow]

Select Control Module 46-Central Conv

Then select under advanced functions 07-Coding

Make a note of the existing values in all the boxes

Then adjust the values to match those from someone with a working Octavia Mk1 VRS CCU (see if someone on here has VCDS and can check what the values are on their own car)

Then click "Do It"

[pants1984]

I've just done the above.

The recode box actually already had the same code (258 - 4 door, 4 elec windows). So that part was OK.

What I did next was go into the adaptations function, and reset the remote control for the key following this guide: http://wiki.ross-tec..._(Generation_3)

After that I kept going up the numbers in the adaptations function as just tweaked any setting I wanted (like turning off the indicator flashing on locking / unlocking the car, etc).

So that's it, electrical problem saga over! Hopefully someone else finds this all useful at some point, and thanks for everyone's help.

(Now begins the defective Weitec damper saga... I'll save that for another thread if Weitec keep messing me around!)

Edited 5 April, 2012 by pants1984

[Sampolainen]

Thanks for this. I hope mine doesn't turn out to be a faulty CCU. How much did you pay for a replacement?

[Dave And Lolli]

Sorry if i am sounding stupid..... But what is the CCU and what does it do? Steep learning curve for this car.....

[Raf_]

central convince unit. controls central locking, windows and loads of other stuff