VW Passat 1.8 litre (saloon, sunroof) - Passat battery drain mystery

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Fri 4 Jun 2010 00:05
VW Passat 1.8 litre (saloon, sunroof) - Passat battery drain mystery - dagorlad73

I have read some great advice on this forum before about the common water-under-seat leak problems and possible battery drains, but after trying all the suggestions I still have a mystery drain on my battery.

First visible problem was water welling up on the floor carpet in the rear (driver-side). Checked plenum area (as suggested in previous posts), but drain holes are fine; no evidence that the battery compartment has ever flooded. Likewise, no problems with pollen filter. I do have sun-roof, so there's a chance water is coming in through there somehow; I checked the suggested inspection points but can see no blockages. (though I am mystified by the 'teats' in the front door slam panels, which apprently need squeezing, according to previous posts...? Or were they having us on?)

Have raised carpets on all sides; ECM module on passenger side is fine and dry (I have no operational electronic problems at all anyway). Did find water underneath rear driver-side, as expected, and a little underneat driver seat; cables that run through these areas appear to be fine though, no corrosion visible, wire shielding appears production-line intact.

The standing drain on my battery is 0.09A (yes, 90 mA); this seems too high, this will drain my 70Ah battery in 30 days. Am I being too picky? Is this normal? I read previously on a forum that the standing drain should be on the order of 5 mA (or 0.005 A)

So I started taking out fuses (even the two power-window fuses besides the relay panel). After taking out *all* fuses, I still have a drain of 50 mA [so, the 'normal' drain should have been about (90 - 50 =) 40 mA.]

Are there any systems that would still be draining the battery even with all fuses removed? Where else could there still be a drain, that may or may not be related to the water underneath the carpet?

How about the alarm system? I couldn't identify a fuse for that, but I know I have one in the car. Does this need re-setting after reconnecting the battery or something similar that would stop the permanent drain? Is there a way to entirely switch off the alarm system at a root?

Any advice very welcome! I'm at a dead end now...

D

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Fri 4 Jun 2010 00:54
VW Passat 1.8 litre (saloon, sunroof) - Passat battery drain mystery - elekie&a/c doctor

On a car of this type I would be looking for a "target drain" of around 50mA or less.As a rough guide ,multiply the battery capacity by 0.6 ,this will give an acceptable draw.Are there any extras fitted?Disconnect any radio/cd/changer if fitted.How old is the car?Some of the later models can take a while for the electronics to go into sleep mode.There may be additional fuses in the ecu electric box ,situated by the wiper linkage ,under bonnet ,driver side.Other possibles are alternator or electronic cooling fan module(if fitted)hth

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Fri 4 Jun 2010 09:16
VW Passat 1.8 litre (saloon, sunroof) - Passat battery drain mystery - Peter D

There are two drain holes for the sun roof and you must ensure these are clear and water can exit the recess and come out at the breather in the door jam. Also remove the cover from the ECU box in the drivers side plenum chamber and check for any water ingress as this is a way into the car as is a failed seal under the box, however you usually get water on your feet. Next disconnect the Alternator and then check the drain. You will hvae to override the bonnet switch and allow several minutes for the ECU's to shut down. Regards Peter

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Fri 4 Jun 2010 10:12
VW Passat 1.8 litre (saloon, sunroof) - Passat battery drain mystery - Peter D

Remove the drivers side kick panel, one screw uner the plastic cover, and check the cabling and connectors for dampness/corrosion. Regards Peter

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Wed 9 Jun 2010 22:24
VW Passat 1.8 litre (saloon, sunroof) - Passat battery drain mystery - dagorlad73

Thanks for the pointers Peter; I've checked under the drivers side kick panel but all is dry and clean;

Next I will try to disconnect the alternator, although it looks like a tough job just to get to the cable connection on the back there underneath the manifold.

I'm a bit unsure about the sunroof drainage: I've looked in the front door slam panels but I can't find any obvious drain holes opening up into that area? I can only see a rubber 'teat' about halfway up the door jam that seems to get squeezed whenever the door closes onto it; it has no opening so can't drain anything. Other than that I just can't seem to find any drain holes in this area... Do you know where I should look specifically for the sunroof drain holes?

thanks!

Andy

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Wed 9 Jun 2010 22:26
VW Passat 1.8 litre (saloon, sunroof) - Passat battery drain mystery - dagorlad73

Sorry, keep forgetting to mention: it is a 1998 VW Passat; quite an old model, it doesn't have any under bonnet lighting so I assume there's nothing draining the battery just from having the bonnet up? (assuming the ECU's have gone dormant after about 20 seconds)

A

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Mon 6 Sep 2010 07:14
VW Passat 1.8 litre (saloon, sunroof) - Passat battery drain mystery - Degga1

water under drivers seat problem on a passat 2000 model had me puzzled for weeks. Found out problem, it happened to be the rubber gromit around the bonnet catch cable had came out. Worth checking solved my problem

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Mon 6 Sep 2010 07:24
VW Passat 1.8 litre (saloon, sunroof) - Passat battery drain mystery - Peter D

Double check the 'duck bill' water vents in the door jam for the sunroof drain. these need to be perfectly clear and water must freely flow out of the sun roof recess. Flsh water through until it run out clear and freely. As has been said the seal under the electonics box is a potential source of your leak. Regards Peter

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