Please help! Battery keeps randomly dying of unknown cause!

[95Mx3GS]

Im not sure if this should go in the electrical, so sorry if I put it in the wrong place. Anyways, 2 months ago I got my soundsystem installed, and was riding around for a month blaring it. Then for the last month, its been on only like twice in the hundreds of trips I've made. This mx3 started in -40 weather, but now for some reason when me and my friend drove to go get some food (the car had no problem starting at my house) the car wouldn't start at the restaurant! grr

I got someone to help me jump it then drove it around for half hour then it was fine.... until now (a week later), today I went to work and in the morning it had no problem starting and when I got into my car a few hours ago it wouldn't start! and it needed like 5 minutes being connected to the booster cables for it to start!

Now, I'm not sure what to do, or what the cause is. I don't think it's the soundsystem since it's turned off most of the time, but there IS a switch under my dashboard labeled 'stm' and i MAY have accidentally flipped it on/off once and this may have drained it ( I made a thread asking what the switch was since I have no clue and the only thing I found out is that if the switch is in a certain position it drains the battery )

Also, recently when at a certain speed/rpm my car has been making this loud whining noise (someone said it could be alternator) but my car is always fine when driving, no energy loss even with high beams and full heat on, the only problem is starting it

So, I sincerely ask you, can someone help me out and tell me what the cause of the problem could be or what I should do?

Thanks so much in advance!

[onlytrueromeo]

Check your battery cables. They seem like theyre loose, or not making good contact. My neg. terminal was loose and my car would randomly die and I had to just move the terminal a bit for it to start. New terminals solved this problem.

Check your grounds to your battery and to your system.

Check your alternator wires to the battery.



It will most likely be one of those 3 things.

[95Mx3GS]

Thanks, I'll try all those, but..

If the battery cables/grounds/wires were a problem, then wouldn't it be impossible to boost my car anyways if they would be loose/disconnected?

[vozaday2000]

not if it was the battery posts because they may not be properly connecting to the battery but when you put the jumper cables on they are giving power straight to the starter, I would clean the battery posts and tighten down the clamps.

[Vanished]

First off, having a sound system in your car (especially a sub) is very hard on your battery. The resistance is constantly rising and dropping, and that battery isn't deep cycle. What probably happened is your battery got abit warn out, and discharged due to the cold weather.

Because it's so cold, your oil viscosity is very high, so your starter has to work hard to get the crank turning. This drains your battery, and if you drain it, it'll freeze. Once it's frozen it'll never work properly again. Drain it competely, freesze, boost, drive, repeat, and your battery will be useless.

Go get a new battery, and i bet your worries will be gone. If it's new, it should be under warranty. Make sure your battery light isn't on, as this would mean your alternator is dying or a belt snapped. i assume this isn't the case as you wouldn't be able to drive for more than about an hour or so.

Good luck.

[Daveb]

That switch somehow sounds like a problem. What I would do is go to a starter/altenator place (I got 1 locally, you can yellow page it) have them test your altenator & battery, takes 2 mins. If tthat checks out can be wiring or starter.

good luck

[cphillips1982]

Dud battery is probly the cause because once a battery gets discharged past a cirtain level it never regains its full charge again and is more or less stuffed, here is a little some thing you can try just in case you have a wire or short issue,,,
1.Get a multimeter and put the probe in the 10amps socket an turn it on in the current reading position. eg DC AMPS
2. turn all acc off including internal lights and disconnect the neg battery lead
3. place the meter from neg battery to chassis

if you are getting a reading of more then say .1 of an amp I would think you would have a problem, to test you have hooked it up right turn the internal light on and you should have around .5 amps running.

If you have a "current leak" then pull your fuses out one by one and wait for the current to stop flowing to point you into the right direction.
note.. do not turn a heavy load on while testing or you will blow the meter fuse. eg headlights or cranking.
goodluck!

[Daninski]

I had the same problem so check the power wire at the starter. I rolled a little of the insulation back to find the wire coated with corrosion. I cleaned it with a wire brush (disconnect the + on the battery first for God's sake) and baking soda untill the corrosion was gone. Now car starts no probs every time.

[cphillips1982]

As for the alternator noise, an isolated RCA cable between you head unit and your amp might do it but if its doesnt that mean you need to filter the incoming power to the amp, these filters are pretty common from most auto stores or off ebay, just make sure it can handle the current you need it too.