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Discussion Starter · #1 · (Edited)
Thought I fixed my m3 yesterday but today it died again at start. No relation to the first fix i dont think. Yesterday i changed the ac belt checked one spark plug to see if its good and put everything back.
The car started fine yesterday and i drove around w/out probs.

Today i went to start it normally pos 1 then 2 (key) all lights were normal THEN something clicked and almost everything went dead. When i mean clicked thats when i turned the key to actually start the car. The last light that was slowly fading away was the airbag light. And the driver window was twitching back and forth (small movements).
Some other sounds from front (electrical) also. Went to the battery and was making faint sound like something burning.
This sucks. My bike has broken down now the car again. Once I sold the 330 everything keeps effin up.
Anyway, anyone experience that on their m3? This could've happen on any w46 dont think its just an m3 problem, or something similar. Thanks

ps sorry for the double thread just need more feedback before i take it in.

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2nd attempt

Took the battery out of the car to test it read very low at ~5. Cleaned the posts which were corroded pretty bad. Put it back on the car re-test it showed 11.98. Power went up! Tried to start the car and same thing happened after pos 2 u hear a click and everything shuts down, int lights slowly fade off. And the battery makes a sound just boils away. Battery is aftermarket interstate brand, crap.
Should i charge the battery all the way up and try it again?
After reconnecting the battery everything is back to normal until u get to start pos.
 

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Sounds like your alternator is going out.
 

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Dash lights coming on/off is a symptom of bad alternator. Windows also start to act like they have their own mind. Speak from experience.
 

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Dash lights coming on/off is a symptom of bad alternator. Windows also start to act like they have their own mind. Speak from experience.
This. Replace your battery. Sounds like it's boiled down and beyond it's useful days.

Once you get it running, use the cluster test or a multimeter and check the voltage with the engine on. Should be between 13-14 volts. Any lower and it's most likely the alternator.
 

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Discussion Starter · #7 ·
Thanks guys. New battery it is. Can anyone explain how the battery had reading of 5 off the car but when reconnected it jumped up to almost 12? Without charging it.

Sent from my LG-P500h using Bimmer App
 

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Thanks guys. New battery it is. Can anyone explain how the battery had reading of 5 off the car but when reconnected it jumped up to almost 12? Without charging it.

Sent from my LG-P500h using Bimmer App
really? thats weird. maybe the meter was not working properly?

anyways if the alternator is bad, you will almost certainly get a battery warning light on the dash cuz thats what happened to me when the voltage regulator went out not charging the battery.
 

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Discussion Starter · #9 ·
I think the voltmeter is working cause I use it alot, checked other batteries recently. No battery light, cant really tell cause the car never actually starts. Im afraid to jump start it, might blow up the old battery. It doesnt look in the best condition. Battery would be the least of my problems. Well i havent really shopped around yet, as with everything for the m3 its gonna be pricey. Im almost positve i hear the fuel pump priming and all.
 

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Dash lights coming on/off is a symptom of bad alternator. Windows also start to act like they have their own mind. Speak from experience.
Yes, the various electrical systems can begin to go haywire when the alternator is going out but this only happens when the car is already running. Before the car starts, you're running 100% off the battery.
 

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Yes, the various electrical systems can begin to go haywire when the alternator is going out but this only happens when the car is already running. Before the car starts, you're running 100% off the battery.
Well I agree that the first thing that should be replaced in this case is battery.

However, if the OP has been running a slowly dying alternator for some time (as it was in my case), a bad alternator would also ruin a perfectly good battery, and the car would not start. The battery simply masks the bigger problem. It took a couple of weeks for my alternator to go bad (one week while waiting the new part), with the same symptoms as the OP's.
 

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Discussion Starter · #14 ·
So a brand new fully charged battery wouldnt even make a click? Alternator only starts making power after the car has started. After i install this new battery i will run at test on the battery and see if it reads somewhere between 13-14. This will tell me if the alt is good or not, as mentioned above by Johnibarr01. The car has ~45,700 miles. Any fuses I should check? Last time we checked the old battery was at 11.98. That should have been enought to crank but no?
 

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Discussion Starter · #17 · (Edited)
The battery wasnt dead tho at least not completely dead. I was driving a day before. Everything seems to shut down when you turn the key to start position after 1 and 2. Soon as you pass 2 you hear a click and everything powers down.

Thanks for the link Txzhp04!
 

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^

That's when the starter is activated and really starts to put a load on the battery. You also have to keep in mind that the electronics are very sensitive to having enough voltage and current. A battery doesn't have to be "completely dead" for the car to fail to start.
 
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