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Discussion Starter · #1 ·
Hi.

I have a M3 from 02 that I have some problems with.
When I bought it the previous said that he has had some battery-problems with the car. And that the battery had been drained a few times.

I drove the car home. About 400kilometres. And no battery-lamp was showing.
But then I saw that the cable to the +terminal of the battery had nearly melted. ( the red cover of the cable)
So it got really hot.

I checked and the cable was a little loose to the terminal.
So I loosened everything and cleaned it, and thigtened it good.
But that didn't help.

If i check the voltage of the battery when the car is of, the voltage is 12.7-12-8Volts.
Which is good.
But when the car is on, it's "only" 13.8-13.9 volts.
Is that a problem?

My other car. A E46 320 has 14.2volts when car is running.


When I start the M3 it's easily started.
And goes up to a idle of 1100rpm.
And then it just "dies"... down to like 100rpm, up to 1100 again.
Down to 100. And does this a couple of times.
And then after a while it dies.


I can also say that when i put the key in and turn it to position 2, I can not even put on the stereo.
nothing happens when I press the on-button.


So what could be wrong here?
Is it the battery?
Why does the cable get so hot?
Is it my alternator?
The voltage-regulator?



Thanks in advice
 

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Sounds like some definite electrical issues. I would have the alternator tested at autozone or somewhere. I believe they can test some things while it's still in the car. An alt can cause all kinds of electrical gremlins and could have been caused but the bad batt connection.

The hot cable could have been caused by the bad connection creating resistance and/or by the alt feeding some residual AC to the system if the regulator/rectifier is going out.

Edit: a fully changed batt should show 13+ volts when freshly charged. Alt should show 14.5ish while charging at 1000+ rpm.

I've found the cheap ciggarette lighter plug volt meters to be very handy for these things.
 

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Discussion Starter · #3 ·
Thanks for your quick answer.
Really appreciate it.

I disconnected my battery yestorday.
And mesured it for a while ago.
Still was 12.8Volts. So it keeps the charge.

I then took of the alternator from the car to see how the regulator looked like.
Here is two pictures of it;

http://www.n0.se/v/f/884e3_imag1116.jpg
http://www.n0.se/v/f/18e64_imag1125.jpg

There is some kind of mark in the bottom where the brushes are.
Is this some kind of maximum ware-sign?

The slip ring looked fine. No scratches. And looked nice and gold all way around on both places.


Is it better to buy a whole new regulator?
Or can I just change the brusches for like 10Usd?


Thanks in advice.
 

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Those pics aren't loading on my iPhone. Might try brackets.

After posting yesterday I actually read that autozone and such won't even test these alternators out of the car because of the water cooling. I've read that the water cooled alt's are not predisposed to repairing.

Edit: oh wait haha. I forgot I'm in the m3 forum. These alt's aren't water cooled are they?
 

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Discussion Starter · #7 ·
I bought a new regulator and installed it.
14.7 volts at the battery.


First it did run the same as before.
But then I saw that the alternator wasnt running.
But after like 10sek, it started.
So mabe the belt didnt had stretched enough.

But now I have other problems.
Now my radio is down.
No power windows.

What can cause these peoblems?
 

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Do they have power? Check fuses.

If the windows work via the switches but not the remotes, you have to program the remotes.

I would personally connect my diagnostic laptop and check for error codes and equipment status.
 

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Discussion Starter · #9 ·
Thanks for answer.


I just hate that you need a old computer with Windows xp
and com-port to use the diagnostic tool.


But i saw something about the kbus that would cause similar problems.
So I Will check that out.
 

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You can get the programs to work with VISTA and Win7, but WINxp in a virtual machine is the easiest.

You could just disconnect the battery for 30 minutes and see if all comes back if the bus got hung.
 

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Discussion Starter · #11 ·
Thanks for trying to help me.

I removed the Kbus-socket from the bracket.
Measured the voltage with ignition on - 0.1V
And started to remove cable after cable.

After I removed some cables, the voltage got 12V.
So I have located a wire that pulls down the entire K-bus.

But now I have no idea witch function it has.

My radio, wipers still dont work.


I disconnected the battery now, and hope that some things will start working again =)
 

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Discussion Starter · #12 · (Edited)
Ok.

So I found a cable that pulled down the entire system.
Disconnected it. But the radio still wouldnt work.

I then removed every thing that had to do with the radio.
Out with the cd-changer, Mk4, Bm54 and the tv-unit.

I then removed the ground-point behind all those boxes.
And just to be sure there was good connection.
I took a sandpaper and gave it a go.

I then put piece by piece back together and measured after every part to see if anything happened to the BUS.

But now everything is connected. And everything work.
So hopefully its working now.
But I've read so many threads now about intermittent problems.
So I just have to wait and see.
 
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