BMW E46 Fanatics Forum banner

1 - 9 of 9 Posts

·
Registered
Joined
·
5 Posts
Discussion Starter #1
Hi, this is my first post here :) I bought a 2002 330ci m-sport a couple months ago (first car), and so far i love it.

It ran quiet and smooth in every way until last night. Last night the red battery light came on for a couple seconds while i revved it, then it went out. A minute later it came on again, and stayed on for 10 minutes before going out again. My dad and i measured the battery voltage this morning and it's fine (11,6V). The generator seems to be working as well. All of a sudden while we were measuring the battery with the engine on, off, revving etc, it wouldn't start. The starter motor clicks, but it doesn't turn the engine. All lights in the car flashes as the starter motor clicks. Battery voltage was still plenty. We push-started the car and it ran fine. Warning lights for handbrake, DSC, red oil light stayed on. We push-started it again, and i went for a short drive to see if the lights went out (they didn't). After a minute, the engine started to run like crap (jerky, like the igntion and injectors were working half-time). Applying throttle had less and less effect, and after barely a minute the engine shut down.

So thats where we are at right now :(
I don't have much experience with cars, and have basically no bmw specific knowledge. I am asking for help here because i know it can get very expensive if i tell the mechanics ''it started to jerk and the stopped'', rather than telling them what the problem usually or probably is. Or maybe if i'm lucky it's something i can fix myself. Any help, theories and advice is very appreciated!
 

·
Registered
Joined
·
81 Posts
11.6V is not fine.

You can jump start it by using the hookup points in the engine bay, a red plastic cap opens to give you your positive terminal and connect your negative lead to the steel hook on the head or somewhere else solid on the motor.

You can change the battery in these cars without having to worry about needing a code for the cd player ;)
 

·
Premium Member
Joined
·
28,970 Posts
You have a bad battery, a bad alternator or a bad engine to body ground or a combination of any of the above.

A fully charged battery should read 12.6 Volts, just because a battery reads 12.6 Volts does not mean it is good, it just means it is charged. A battery test needs to be performed to verify if the battery is actually good. A poor mans battery test is start with a fully charged battery, turn the headlights on in the vehicle with the engine off, after 2 minutes, the battery should be at 12.2 Volts or higher, if so the battery is at least in pretty good condition.

A battery below 12.0 Volts is effectively 100% depleted of power it is capable of supplying.

A proper charging system should provide 13.5-14.5 Volts to the battery while the engine is running with accessories on.

I had a bad battery, it had a bad cell, it caused all sorts of havoc with the E46, lights on for ABS, Traction Control, Brakes. The dash lit up like a Christmas Tree. Thought the alternator was also a problem, but a the end of the day, just the original battery was bad in under 4 years.

I do not personally trust any battery that is over 4 years old. Some may last far longer, but after 4 years, I get nervous and constantly test the battery 3-4 times a year.
 

·
Registered
Joined
·
5 Posts
Discussion Starter #4 (Edited)
Thanks for taking your time to answer! I spoke to my moms husband who's been driving bmw for decades, and he is 100% sure it's the battery as well. I thought as long as you had enough battery to crank the engine, it should be enough. The guy i bought it from said he put a new battery in not too long ago, but i'll replace the battery and come back:)
 

·
Premium Member
Joined
·
28,970 Posts
If the battery was really replaced, it may actually be fine. The problem is when the battery is not fully charged or actually bad, the cranking Voltage drops too low when starting the engine and the modules have a problem communicating with each other. The DME shuts down the multiple spark triggering routine and then errors pop up and the engine may not run properly.

For example the FSU or blower resistor could be bad and draining the battery causing these problems. Get the battery charged and tested as I assume a battery is not cheap in your area of the world, like most car parts. If you have VAT this is a big hit along with a recycle fee!
 

·
Registered
Joined
·
5 Posts
Discussion Starter #6
I replaced the battery and everything worked, it did recieve some charging at one point. But today while out testing the warning lights came on and it eventually died just like before. So i guess it's either the generator or the charging relay. I tried measuring the generator on the nut where the thick red cable is attched to the back of it (i assumed it's the + cable), but i got nothing. So the next move is to get a new generator? Or could it still be the relay? I am at least very happy that it's simply a charging problem. I would NEVER have guessed that all the warning lights and the engine jerking and dying was simply because of low voltage.
 

·
Registered
Joined
·
2,445 Posts
Yea, alternator is bad. Do you have a multimeter? While running, you should measure 14V at battery. I bet yours will be basic 12V from battery itself.
 

·
Registered
Joined
·
5 Posts
Discussion Starter #8
It drops almost 1V while idling. I'm just about to remove the regulator to see exactly what it looks like, so i can order/buy a new one.

Thanks//Mannen
 

·
Registered
Joined
·
5 Posts
Discussion Starter #9
I replaced the regulator with a new one, including new carbon pins(?). It has idled for 15 minutes now, and i have 12,66V on the battery, and 13,5 while idling! :D. It was the carbon pins that were very worn out. Thank you everyone for the advice! If i hadn't bought a new battery, it would have cost only about 60$ and an hour of work.
 
1 - 9 of 9 Posts
Top