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Discussion Starter · #1 ·
As the title says, my 2003 GLX 4motion has a battery killing drain.

Story goes, I'm the new owner of my Passat. Got it from some very untrustworthy people who said nothing was really wrong with it (I knew it was a lie, but I needed an awd car for the icy winters and crappy Michigan roads).

Car had hit a deer, bumper is held on by zip ties (my doing), sunroof works (but occasionally on its own), fuse in the radio was popped, one wheel is 2 inches bigger than the others, headlights barely work and don't point forward, cruise control doesn't work (or I haven't figured it out).

I don't know what is draining the battery, it's brand new yet cheap. I just bought a new charger for it that will take a day to charge it, and a multimeter to test out different spots. Before this, you could leave the car to sit for a week before the battery was low enough that it needed a boost, now it's completely dead to the point where the odometer doesn't show. I read the codes before making a 5 hour trip to my new house, but it only threw up torque converter codes.

I might pride myself on knowing more than some on cars at my age (21), but this electrical nightmare has put me in my place so far. I need the car back for the winter, otherwise I can't get much other than a job at McDonalds, and I'd rather not.

Does anyone have any idea what to check? A good guide for this?

TL;DR version: My crappy Passat has a battery drain that I have no idea how to fix.
 

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Put the charged battery in the car. Connect an ammeter in series with the charged battery, in either the + or - side. If everything on the car is turned off (including interior lighting), the parasitic drain (the current that's flowing to maintain the car's computer memory, and perhaps the radio's memory as well) should be low, on the order of .02 amps. If it's more, something's using electricity that shouldn't be.

To dig deeper, again with the battery charged, installed, meter connected, and everything turned off, pull the car's fuses one by one. While there are some unfused circuits in the car, it's likely that pulling some fuse will cause the meter to show that the drain was happening in that circuit. Then you have to investigate the electricity consumers and wiring that are fed by that fuse to find the fault.
 

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Discussion Starter · #3 ·
Sounds like a days worth of troubleshooting, sounds like a lot of fun.

Thank you, I'll see what I can figure out in a few days when the multimeter arrives
 

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To dig deeper, again with the battery charged, installed, meter connected, and everything turned off, pull the car's fuses one by one. While there are some unfused circuits in the car, it's likely that pulling some fuse will cause the meter to show that the drain was happening in that circuit. Then you have to investigate the electricity consumers and wiring that are fed by that fuse to find the fault.
Better: Faster, less invasive, and more accurate:
Once the existence of a draw has been confirmed (by measuring it at the battery), instead of doing the 'pull the fuses' method (tedious, time consuming, and can introduce other errors), measure it at the fuses!
http://www.autonerdz.com/yabbfiles/Attachments/HowtodoParasiticdraintestacrossfuses.pdf

First question, before you start troubleshooting):
Factory or aftermarket radio? If aftermarket, what brand?
 

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Monsoon radios with trunk-mounted amplifiers sometimes fail so that the amp draws power even when the radio's turned off.
 

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While you're waiting for the multi-meter I'd start by checking all the wiring in the damaged area of the front end, especially the headlights. There are also a few sensors on or near the radiator or supports, etc that would be worth looking at. Basically just look for any obvious physical damage to wiring, ground points, etc.

Both dbrick's and cuppie's methods will work but to measure the voltage drop across the fuses you'll need a decent meter and more importantly, sharp probes that can make good contacts with the fuses. Most entry level DVM's come with somewhat cheap, blunt-ended probes and they may not be able to make solid contact with the fuses while they are still installed.

Finally, you probably know this but you may be in need of a new battery at this point. If the present battery doesn't hold a charge, I'd try to exercise the warranty and hope the store allows you to use the rebate money to get a better battery.
 

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Factory, blew shortly after I got the car.
Monsoon radios with trunk-mounted amplifiers sometimes fail so that the amp draws power even when the radio's turned off.
There is this.
There's also the (theoretical) possibility that, because of how that amp works, that a bricked headunit (radio) could cause the amp to stay on. And, it's a big load.

If you haven't yet bought a DVOM (it reads like you might have one on order?)....
This one is a very good bang for the buck: https://www.amazon.com/gp/product/B000KIMHRQ/ref=ox_sc_sfl_title_14?ie=UTF8&psc=1&smid=ATVPDKIKX0DER
Also worth mentioning is Klein Tools. A $50 meter from them (can pick up at, say, Home Depot) is actually quite nice for the price.
 

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Discussion Starter · #12 ·
I unplugged the amp (took a like 10 minutes to find the location through the internet), would that mend the issue if that was causing it?
 

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Discussion Starter · #13 ·
At this moment, with my glorified battery maintainer, it only managed to get to the point where the dome lights and hud turn on. Turning the ignition makes click behind the dash, not in the starter.

Edit: after 10 hours on "charge". Really putting that $42 to work...
 

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Discussion Starter · #14 ·
Update.

After unplugging the amp, the starter finally received enough power to engage for a moment. I also left the car door open for an hour by accident, so there was drain while it charged.

So, I think I figured out the issue without even having to test anything, we'll see in a few hours when I try to start it.
 

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sunroof works (but occasionally on its own)
Reasonably common problem. The sunroof potentiometer, connected to the knob in the roof, gets flaky from contaminated/worn contact between the movable wiper and fixed carbon resistor, or sometimes the spring contact force is just weak, and re-flexing the wiper corrects it.

The battery issue: Once started, what is the Voltage across the battery terminals? Should be around 14 Volts.

If you get the battery charged, then disconnect a battery cable (either one) does it hold the charge and start the car the next day?

Measuring current at the fuses: besides a quality DMM, you'd need a charged battery to get a realistic current measurement. But if the battery drains that fast, the current has to be substantial. Instead of interpreting milliVolts on a chart, I'd suggest soldering an instrument bulb across a blown fuse, which you would plug in place of removed fuses. If it lights, there's the draining circuit.
 

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Discussion Starter · #17 ·
Reasonably common problem. ~ended up sorting itself out, hopefully for good~

The battery issue: ~Idk if the battery will charge, which will be the death sentence for this car (I'd sell it on the spot). I'm not sinking another $125 into a battery, I don't have that money.~

If you get the battery charged, then disconnect a battery cable (either one) does it hold the charge and start the car the next day? ~I'll try that out if I get there.~

Measuring current at the fuses: ~Interesting method, though I'm inexperienced with soldering and only have a large solder gun.~
 

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Discussion Starter · #18 ·
Good news, it started.

Bad news, it runs a little rough, the passenger side of the engine has steam/smoke coming up from around the exhaust, and I smell burnt rubber when I turn on the air.

Still need to figure out what's draining the battery, but I've made headway and I'm happy so far.
 

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So you charged the battery and it started. That is good.

The smoking/ burning smell could be coming from oil dripping onto the exhaust. Pretty common with these cars. Usually caused by leaking valve covers. It will run rough for a bit until the computer resets itself. It lost it's memory from low or no voltage.

Now sell the car in it's running condition and try to recoup some of the $ you spent buying it.

Unfortunately this car sounds like a heap (you knew it was a shady deal from the get go) It is going to run you dry
($ wise) really quick. Going on just what issues you have mentioned there are sure to be many; many more you don't know about that are lying in wait. Trust me. Those issues will present themselves at the most inopportune times.
 

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Discussion Starter · #20 ·
Battery holds a charge now.

Had just enough juice last night to start, and just enough at 8 this morning (5 hours) to turn the starter a few times (before this it would be drained by morning). At noon, it had enough charge that the starter didn't struggle to start the car (remember that my charger is a glorified maintainer). I believe I solved the biggest drain and the secondary drain, but there is still a third drain as the negative charger terminal sparks faintly if moved (idk if that's normal).

I have the ability to sell it, I just don't want to if I can get it going and stop the drain. The other issues will be sorted if they pose a threat to the integrity of the car.
 
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