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Something is killing my battery

Recently, I went to jump my sister’s car off because it had died. Her boyfriend, not knowing what he was doing, grabbed the jumper cables, while I was hooking them to my car, and hooked them up to my sisters car. He hooked them backwards. My car immediatley died and sparks flew. Well, I knew he had to get me a new battery, which he did. I type all this to say that something is still killing my battery. I have had the alternator checked and auto zone said it was fine. My radio still does not work, so I took out the fuse hoping this would stop the problem and it hasnt. Do any of you have a clue on what might be the problem. I would appreciate any input before I take it to a shop and they charge me an arm and a leg to even do a diagnostic check. Thanks!

Go give your arm and leg. The best advise isn’t always free.

Many years ago (1960’s) I had a dealer do the same thing. My car was waiting for a new part (from Scotland) for several months. I told them I wanted a new starter and generator as well as anything else that might turn up in the next few months. The mechanic said no problem just reverse the leads back to were they should have been. This time smoke poured out of the engine compartment. They gave me back my loaner (nice car by the way) and in a few days had the new parts in an installed.

My story was easy. Your going to have a far more complex issue with modern electronics.

My advice, sorry but someone is going to need to pay that arm and a leg to diagnostic the probem(s). We can’t do it from here.

Taking out the fuse is not going to make the radio work, in fact it will guarantee that it won’t work. It does sound like you’re going to have to pay someone. Unfortunately, as simple as jump starting is, it should be treated like surgery… one person in charge and checking everything. Sorry, this must suck.

I think she meant she took the fuse out in the hope that the dead radio was causing the parasitic current drain, and that this would stop it.

You’re lucky that’s all the problems you ended up with after that. The best way to diagnose this would be to put an ammeter (a meter that measures current flow) between one of the battery terminals and the cable that normally attaches, and measure the current being drawn from the battery with everything off. If it is too high (there will always be a little bit of a drain on a modern car), then start pulling fuses until the drain stops. Then you know what circuit is the problem.

If you only barely understand what I’m describing, then this is something you really should not try doing for yourself. I think you will have to spend a little to find out what’s going on here. You may be able to get by in the meantime by disconnecting the negative battery cable each night to prevent the current drain. And a replacement radio can be had on ebay if you just want to replace the factory radio. I suspect part of one of the car’s computers may be damaged, but don’t quote me on that. You would be better off finding a good local mechanic and not going to a dealer or a chain like Midas.

Good luck and post back with what was the problem.

How many amps is too high? I will try this out. I was hoping that my computer was not damaged. But it appears it may be :frowning: I appreciate your input. Very helpful.

It should be far less than an amp with everything off, key out, doors shut. Probably no more than 100mA (1/10 of an amp) But I couldn’t tell you for sure what the max should be.

Normal current draw while a car is parked and things have gone into the sleep mode should be less than 30 milliamps for most cars. More than a 80 ma. draw is cause to look for trouble.

If the alternator was checked while it was removed from the car then you need to make sure the alternator is working ok while running normally in the car. There could be problem within the wiring to it so it may not be working. Be sure all the fuses are ok under the hood and in the dash panels.

Make sure the radio is getting power to it. If that checks out ok and the radio doesn’t work then you will most likely have to replace the radio.

I think your sister’s boyfriend owes you big time.

Thank you soo much for your help. Will check that out in the morning!