"Foreign" Car Question

This actually concerns a friends VW Passat but I have asked the question on a VW group for him and got no response. It seems to me that we have some
knowledgeable people on here and the problem (I think) could equally apply to any make of car.
His Passat is only a few years old and has develpoed an electrical current drain. It has been into the VW agents a couple of times and all they can tell him is that his battery is fine, they can find absolutely nothing wrong, but his current is draining away (this bit he knew). It is so bad that on a couple of occasions he has had to call out roadside assistance to jump start it and now carries one of those emergency power pack thingummys in the boot.
I am wondering whether anyone on this group has experienced similar problems and can shed any light on it.
--
Keith W
Sunbury on Thames
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Many years ago I had a similar problem with a Sierra. It took a while to find out that the boot light was staying on when the hatch was closed!
A possible suggestion is disconnecting the positive connector from battery terminal and then connecting an ammeter between the terminal and +ve connector. There will be a current if the battery is draining. Now remove and replace, one by one, all of the fuses to see if the current suddenly falls. If it does you will have narrowed down the items to look at.
Worth a try? Lenny

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Unfortunately it is an estate so that problem would be obvious. However, I have heard of some cars having a light under the bonnet so I will get him to check that out. Thanks.
Keith W

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Keith W wrote:

Keith, You(or your mate) needs to take the other section of Lenny's reply. Finding electrical problems on a modern car needs logical elimination combined with understanding what you are doing. No quick fixits in my experience.
Bob
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It
Could
Be
Anything.
Best thing he can do is check out how much current is being drained using a multimeter and try and track it down to individual circuits using a wiring diagram. It may just be easiest to get an autospark to do it as the wiring diagrams are often difficult to come by (the haynes ones are incomplete, even in the good old days of relatively simple cars and relatively comprehensive haynes manuals).
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Check All the door switches. also the boot one , these bloody things can play up and nobody thinks of these little things just sitting there waiting to take the power out of the batt,(i bet it is one of them playing up as it drfains the power over night,) good hunting..
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