03 bmw won't hold battery charge

I have had this car for years and just about two weeks ago i had to start jumping it. So i bought a new battery then i just bought a new altinato. I have had both tested and the altinator is perfect and so is the batter. But when i start the car it will run but after a while the battery is dead again. If i let it stay parked over night the battery will build up enough juice to run again but the same thing happens again. What could be causing it to lose amps while running like that besides the altinator since i know that isnt it.

You have a short somewhere. You need to start pulling fuses one at a time to see if you can isolate it.

Well we have checked the fuses and they dont have that bad of a draw. What kind of a short do you think it could be if it isnt the fuses?

Could be anything. Stuck relay, chewed or melted wires ect. Bring it to a trusted auto electrical shop in your area. This type of thing will drive you nuts if you don't have the right equipment to find the short. Might cost you a few hundred to find it, but it might be the best money you ever spent. I speak from experience.

Originally Posted by SJBimmer

Could be anything. Stuck relay, chewed or melted wires ect. Bring it to a trusted auto electrical shop in your area. This type of thing will drive you nuts if you don't have the right equipment to find the short. Might cost you a few hundred to find it, but it might be the best money you ever spent. I speak from experience.

It's not the right equipment to find a short, it's knowledge and experience. That's why I love electricity. Need just a vom to check things out.

I would also check to ensure the negative ground wire is solidly attached to the car.

Originally Posted by GoForthFast

It's not the right equipment to find a short, it's knowledge and experience. That's why I love electricity. Need just a vom to check things out.

Actually, it is important to have the right equipment. Poking holes in wire insulation when connector access is difficult, or the wire runs through enclosed metal sections of the car, is not the right way to go. My shop had a machine that was a sophisticated version of the method used here. Knowing you have a short by using a VOM, and finding where the short is along the wire are two different things.

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