Something is draining my battery

This was at the end of Oct. I came out and my 2012 SEL TDI would not start because of a dead battery. Because this was repeat of what happened to me in May, (Dealership could find nothing wrong.) I had AAA pick up the car and tow it to the dealership. When I had the problem in May, I had the battery replaced with a Duralast, not a VW installed battery.

So the dealership has the car. First thing they said was that my less than one year old Duralast battery had a dead cell so that was replaced. They charged the battery and by the next morning the new battery had drained. After about two weeks, they said I had a defective radio/navigation system (it is a Fender audio system) that was drawing 2095mA and that was the problem. Would I like to replace it with a refurbished unit for $2646.10? Of course I said No. Since the radio/nav was out of the car, I had them to leave it out as I planned to replace it with an aftermarket unit.

So I picked the car up on Friday. I ran a bunch of errands on Sat and had no problems. Car sat on Sunday and and I came out to start the car on Monday morning and the battery is dead. It is beyond dead as even AAA cannot jump start it. So once again my car is back at the dealership. It has been there for a week and all I hear is the dreaded "We have never seen this kind of thing before".

I am at the point where I am asking you what should I do????

Ron M

Intermittent draws are the worst because they are not constant and easy to find. Pay special attention to all components in the car and see if any are acting weird for a clue to help the techs working on it.

Door harnesses and trunk harnesses can have broken wires touching after being moved one time, and not the next. I had an Audi S6 Avant that developed a problem in the hatch harness. I luckily noticed it one time when I was in a hotel far from home going to a class. I went to grab some luggage out of the car, and as I shut the hatch I noticed the radio display lighting and dimming almost like a heartbeat. I was thinking here I am 600 miles from home with a car that might die overnight. I opened the hatch again and massaged the wire harness as a hunch and the radio behaved itself again. Car was fine the next day.

Check your car after dark randomly to see if any lights are on that shouldn't be, maybe even really dimly. Door latch switch failures intermittently are not unknown

On Passat, engine wire harness chafing is not too uncommon either, and the engine does move which can cause intermittent (at first) problems.

On really stubborn intermittent draws I have parked a car in an unused corner of the shop with all latches tripped and doors and hood open. I put a light on the battery cable for easy reference and put the car to sleep. When the intermittent happens the light will light and you have to run over and start pulling fuses and relays till you find the live circuit.

I found a really hard one that way on an Audi with a very intermittent window closing relay that would come to life and try to close all the window and sunroof, at least till the battery went dead.

It takes patience and luck to find the draws if they are intermittent enough. I had an Acura that the wife drove. It would draw the battery stone dead maybe one time a month. I tried in vain to cure it and gave up. I sold the car that way and did inform the new owner of the demons lurking within. I really didn't like the car for a number of other reasons, or I might have kept at it to the end.

sounds like a stuck control module, run a test with VCDS- oh and always remember to get the key fob away from the car as I leave the keys in the ignition on all my rigs when at home, but the Passat will drain the battery flat dead in one night if left in the car

The 2 amp draw shouldn't be too hard to find hooking up an amp meter and pulling fuses. According to the dealership it is a constant draw. not a bulb for sure, perhaps a sticking door lock actuator.

Isn't the process measure voltage across fuses once the car is asleep, any one that has substantial voltage compared to the others also has current flow (fuses heat up with current, that heat is a voltage drop due to the resistance).

Either that just start pulling fuses one at a time each night and see what one it is.