Q: Car keeps needing to be jump started after sitting for a day or two

asked by on December 29, 2016

I keep having to get my car jump started after the car has sat for a day or two. I have had the battery, starter, and alternator checked and everything is fine. Also, the battery was just replaced in July. I took it to Pep Boys and they suggested based on what I told them that something is draining the battery and it may be electrical. So I left the car for them to do a check. Well, they tested everything including hooking it up to a machine, and they said that they can't find anything wrong. The only thing they said was that the brand battery I had in the car was not the best brand, so I said are you saying the battery is not compatible with Volkswagen and they said no the battery is good but they don't really recommend the brand. I don't know what it could be at this point. I don't know if I should by another battery or get a second opinion. Do you have any ideas/suggestions as to what the problem could be?

My car has 134000 miles.
My car has an automatic transmission.

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Pep boys is probably right about there being a drain, but they may not have the know-how or equipment to detect it. Chances are your CAN (control area network) is not ’going to sleep." The can is the line of communication between the control modules on your car and it stays on for about 30 seconds after the last person gets out of the car and closes or locks the door. The modules will draw about 400 MA from the battery until the Can goes to sleep at which point the draw drops to about 100 MA. (milliamps) Any draw over 200 MA with everything off is too much. Failure of the CAN to sleep can be caused by any switch like a door, hood or trunk not being off, or by a bad control module or even a low battery. Any signal from a remote will activate the CAN. I’ve seen cases where car owners would allow their toddler to play with the car keys and their repeated pushing of buttons would continually reactivate the can on the car in the garage and run the battery down. Your car needs to be checked out by someone who is well acquainted with the electronic systems on a VW. You can contact Your Mechanic to have a qualified technician come to your home or office to check out your battery drain and let you know what is the solution.

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