Passat loses battery charge

If I leave my 2005 Passat for a week, the battery goes dead. The dealer says this is normal and I must disconnect the battery every time I leave it for more than a few days. They have searched for an electrical “leak”, and I have had 3 batteries in 3.5 years. Is there any device out there that can prevent battery leakage? Shoud I keep looking for the leakage source although no one can find it.

Dealer is full of ....   

Now if you are leaving it for a month, maybe they have a point.  It should be fine for a couple of weeks.  BTW for a while VW was giving away a solar charging gizmo with a new car.  You can buy one yourself.  As long as your car is parked where the sun will get to it, you should be fine a year later.

I guess we can rule out your battery as the problem, so that leaves the charging system and the DARK drain.

Most auto part stores can check your charging system and will catch most charging problems.  Often they will do it for free.  However I suspect you may have a DARK drain, pulling more power when your car is turned off than it should.  Do you have an after market security system? After than it is a detective job, checking out circuits, measuring drain (both right after you turn it off and hours later.)  A little experience here can greatly shorten the job.  Good Luck.

Wow, what great dealer service you have there. NO IT IS NOT NORMAL to drain a bettery in a week. I remember VW having discharge issues with the Toureg which were caused by the navigation system.

We have no after market anything–we have had 2 dealeres check this out–the one who sold us the car (the one who said it is “normal”) is no longer a VW dealer (surprise there). The next dealer proved no better at finding the problem and also tried to sell us tires we did not need). We called VW HQ to “register” this as a problem before the warranty expired. Is there any way they can help since their local people seem at a loss?

no navigation system…there must be somthing draining this but where to look? See above 2 dealers tried and found nothing.

Sounds like you will need to find this problem your self, Do you have a battery charger? If so, disconnect the RED battery cable (you can leave the black ground on) and hook up the charger leads to the car leads (Black & Red) (not the battery). If the red lead is going to touch any metal part in the car, cover it in masking tape to insulate it… or a cloth or something. Key is not in the ignition by the way.

Turn on the charger at the 2 amp setting (if you have a choice) and look at the amperage gage on the charger. It should be zero, or very low. My guess is it isn’t and is reading something. Open the fuse box and start pulling fuses until you find the curcuit that is sucking down all the power, then check out that circuit. Or tell the mechanic…

If the amperage is low (like a trunk lid light) you may need to put a radio shack multimeter in the circuit, set to read amps.

Good luck, electrical problems are nasty

Thanks for taking the time to explain–we will try this.

First up, find out how much discharge you have. Hook an VOM up between a terminal and the battery cable with it in the high dc amperage setting. See what it reads. That should tell you how much out of “normal” it is at least.

We called VW HQ to “register” this as a problem before the warranty expired.

Since you appear to be on new car warranty, then it is time to check out your states lemon laws.

The battery drain could be something coming on after the car is parked. Anytime after one hour of being parked, and several times afterwards, sneak up on your car. Be careful not the “awake” the alarm. Closely look for any lights, and listen for any sounds. If you see, or hear any, take note of type and location, and report to your independent shop/mechanic.

If you disconnect the battery, the engine computer will have to relearn some finer things of operating your engine, and the radio may have to be reset--------by the dealer (for $ ) !

There are things that don’t have fuses, which can drain a battery ----- the starter cable and solenoid, and the power cable connection to the alternator, or the alternator internally.

You can try to stop the drain, when parking for an extended time, by pulling all the fuses except the ECM (PCM?) engine computer, and radio fuses.

Here is a good article for the DIY using a multimeter. It has good pictures which enhances the article:

You can find more articles if you go to, search for “car battery drain” (You gotta use those exact words).

Definitely not normal. The dealer is just trying to get rid of a problem he cannot solve.

In the old days, we put a voltmeter in series between the battery terminal and cable. 12-12.6 volt reading meant a drain. Pull fuses and relays until the reading drops to below 9 volts. These days, with so many semiconductor circuits on the car, the voltmeter test is a bit less definitive, so if your meter will measure up to an amp or so when wired in series, that is a better tool for the job. Be sure you have eliminated the easy stuff, like a glove box or trunk light that is staying on.

Some drain is normal, but it should take at least six months to drain a battery to where it won’t start a car. It would be good if you could measure the normal drain on a similar car so you would know what your target is.