2001 passat 1.8 battery drain
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  1. #1
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    2001 passat 1.8 battery drain

    New to the site, I'm frustrated out of my mind with this problem. I've had my 01' passat for a year now, and I absolutely love driving it, good thing too, because I would have sold it by now if it wasn't such a great drive. About 3 months ago, my battery started to drain over night down to nothing. I just had it in to the shop and had the drain traced to fuse 14, which seems to be a common problem with this model. The battery is brand new, as are the cables.

    I noticed that my alarm doesn't sound when I lock the car with the key anymore (which it used to do). I also pulled fuse 14 and came back the next day and it started fine. So does this mean the alarm is faulty? How the heck do I fix this? I've also read that people have common issues with the comfort control module from moisture getting under the drivers seat. I ripped up everything and it is still bone dry under there.

    I just found a thread today on another site that says my aftermarket cd deck can cause this problem because of "clips" that are not seated correctly. Can anyone go into more detail on this? I had my cd deck pulled out several times over the last few months to replace a fuse and I also had subwoofers installed by best buy. This seems like a promising answer.

    I've searched all over and made calls, no one seems to be able to give me a straight answer. Please help me get back on the road!

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  3. #2
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    We can't give you a precise answer because we don't know.

    What you've found out so far is that something connected to fuse 14 is defective, and allows current to flow. It could be the alarm (maybe something internal has fried), it could be something else connected to fuse 14, or it could be something in the wiring or connectors which live downstream of fuse 14.

    All those circuits must be tested. And it isn't enough to just test the load device (the bulb, the alarm box, whatever else is powered by fuse 14) at the end of the wire, because the fault could be in the wire before the load. It would be nice to have an ammeter to put in series with each wire coming off fuse 14, as one of those wires will have too much current flowing. The fault is somewhere in that circuit.

    Some minor current flow is normal in some circuits, as to keep the radio memory alive. Your car has a bad load, or a short to ground, or something like that...somewhere.

  4. #3
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    Have you scanned the CCM for faults with VAG-COM? That could lead you to the problem. After a certain amount of time the CCM goes into a "sleep" mode where the CCM current draw is minimal. If a switch if faulty, the CCM can remain in the active mode using considerably more power.

    Also, measure the current drain in the fuse 14 circuit (and all fused circuits if you have time). You can do this by measuring the voltage drop across each fuse and compare it to the table below. Just ratio up the values in the table for other mV readings. If your battery is draining overnight, then you have a significant drain. The normal drain on the battery is in the 65 mA range.

    Have you checked that your glove box and trunk light are shutting off?


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    All my lights are shutting off correctly. My mechanic told me the drain from fuse 14 was 150mA. I don't have vag-com, so does that mean I need to just break down and take it to a vw dealer?

  6. #5
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    A 150mA draw plus say another 65mA for normal load on the battery should not drain the battery overnight. That's only about 5Ah in a 24 hour period and hardly enough to affect say an 80Ah battery over night. I would guess that if your battery is being discharged in say a 12 hour period then your draw has to be in the several AMP area not mA.

    Are any of your amps, CD player, or other electronics warm to the touch after the car is off for an hour? Again, get a quality digital voltmeter and measure the voltage across each fuse by using the needle point probes. It's easy to do.

    Yes, you will need a VAG-COM to check the CCM. Post your location and maybe a member with a VAG-COM can help.

  7. #6
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    Rule of thumb is that normal current draw should not exceed 50 mA after all the modules have timed out(gone to sleep) Depending on the battery 150 mA will cause a no start if left to sit for a day, now if it is a quality batttery with a good charge it may have to sit for a couple of days before it becomes an issue.

    Why does your cd player keep blowing fuses??

    The factory alarm is tied in to the radio, it is possible that something is messed up with you installation and causing your alarm issues...actually blowing radio fuses coupled by a Best Buy installation is a sure recipie for disaster.

  8. #7
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    My radio blew a fuse once this summer, right after the best buy install. I haven't had any issues since then. The amp/speakers/subs are not draining. The alarm light that is built in to my kenwood deck is blinking as well, which leads me to believe that is is working properly. I've gone through everything with the volt meter as you recomended, my neighbor has a garage full of car toys so I had him help me out. I also had my battery checked out and it is like new.

    The problem is definitely fuse 14, is there any way besides vag-com to check the door/hood/trunk to see if they are not shutting or locking properly?

  9. #8
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    The control module in each door handles the I/O between the devices in the door and CCM. The communication between the door module and the CCM is a via a CAN. So, without pulling each door panel off you cannot check the status of the door switches. The hood and trunk switches run directly to the CCM.

    You can get wiring diagrams at http://volkswagen.msk.ru/index.php?p=page09

  10. #9
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    1.8P,
    KenB is correct, to drain the battery overnight you are looking at amps of current draw, not milliamps. I recommend pulling fuse 14, putting an amp meter across the fuse terminals, close the doors, lock it etc., whatever you do at night and see if you get current flow in the amp range. If so, start disconnecting anything that's on the fuse 14circuit, one at a time, until the current draw drops into the ma range, and you'll know what the problem is. You can also do this by disconnecting one of the battery cables and putting the amp meter in line between it and the battery. It can be time-consuming, but you will find the problem. I once had a Caddy that did this and I traced it to a short in the power seat switch caused by rust bridging a power terminal to ground.

  11. #10
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    I am going to venture a guess that when you remove your key from the ignition you are not getting the "clunk". I found out (by leaving the key in the ignition overnight) that if the key is left in, even though car is off, full power is applied the electrical system. THis could be why your alarm is not sounding as it thinks the key is still in the ignition. I would start there.

  12. #11
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    I also had a battery drain earlier in the week, it was my amp.

  13. #12
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    Quote Originally Posted by 2KB5 View Post
    1.8P, I recommend pulling fuse 14, putting an amp meter across the fuse terminals, close the doors, lock it etc., whatever you do at night and see if you get current flow in the amp range. If so, start disconnecting anything that's on the fuse 14circuit, one at a time, until the current draw drops into the ma range, and you'll know what the problem is.
    This is exactly right for determining which circuit connected to fuse 14 has the problem.

  14. #13
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    Quote Originally Posted by 2KB5 View Post
    1.8P,
    , to drain the battery overnight you are looking at amps of current draw, not milliamps.

    Completely incorrect. Have you ever left a dome light on in a car overnight and the next morning find that the car won't start because of a dead battery? Happens alot on older cars because they don't have computer controls that shut off devices after a certain amount of time. The average dome light in a car draws about 350 mA to 600 mA...point is that a mA draw can and will kill a battery overnight.

  15. #14
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    Well, I can't say what it takes to drain a battery overnight, but I know my total draw is somewhere around 250mA and it is draining it if I let it sit for a day.

    I bought myself a meter, and I'm going to start the trials tomorrow. Does anyone know exactly what's on fuse 14? According to my manual it is the alarm system, the locks, windows, and sunroof.

    1.8P, I recommend pulling fuse 14, putting an amp meter across the fuse terminals, close the doors, lock it etc., whatever you do at night and see if you get current flow in the amp range. If so, start disconnecting anything that's on the fuse 14circuit, one at a time, until the current draw drops into the ma range, and you'll know what the problem is.
    How do I go about disconnecting the locks, doors, windows...etc?

  16. #15
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    The only thing you can do is to start disconnecting components directly where they plug in. I will look at a wiring diagram in the morning and give you a few more ideas. You could probably measure each independent circuit where they connect to the ccm and see what is staying on that way

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