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pawcio 03-25-2010 04:18 PM

Diagnosis: battery, starter or alternator?
today my car didn't start. well it started several times today but not the last time. no turn over, only a clicking noise. battery, starter or alternator? i'm hoping its the battery but i guess i'll have to see later today.

i plan to test it when i get back from work.
is my logic for these three scenario's correct?
1) get boosted, car does not want to start ---> starter
2) get boosted, car starts but dies after several minutes? ---> alternator
3) get boosted, car starts and keeps running ---> battery


p.s. how long would it run just off the battery before it stalls if the alternator is done for?

Junaid 03-25-2010 05:55 PM

if the battery is completely dead then after you drive it will not start, but boost it and drive for a bit and then park it and see if there is more juice then before, if so then its battery since alternator is trying to charge it, alternatively get a multimeter and check the voltage with the car running, it should read 14V

pawcio 03-25-2010 06:01 PM

the thing is the car isn't at my house right now. when i get it boosted and it runs for while, i'll try to drive it home, shut it off and try to start it again. if it doesn't start i'll assume its the battery and get it checked and replaced. i'm really hoping its the battery. don't want to find out that its the alternator while on my way home.

i'm still wondering though, how much time the car could run after boosting if the alternator is bad. the battery isn't new so i'd assume a few minutes at idle and it would stall.

Junaid 03-25-2010 06:06 PM

im not sure how much time you will have, my guess is 15-20 mins, depending on how strong your battery was before.

pawcio 03-25-2010 09:29 PM

ok, so here's an update. i'm slightly more confused, but i know its not the starter.
so got it boosted and it idled for 15 minutes or so before i headed home. once at home it didn't start again. so then i'm thinking battery.
i went to get it checked and the voltage was 11.69V and with 289CCA, should be 630CCA, but the conclusion was "battery is good, but low on charge, charge the battery and return to vehicle"
so i got it charged and tested again and it should be good. this would point a finger to the alternator, no?. btw, i noticed that the date stamp on the bettery was Nov 08, so its only ~16 months old.

if i got boosted and drove home the, 30 minute drive from where the car was should have given the alternator enough time to charge the battery, no? anyway, its charged now, i will install it tomorrow see if it starts and then see if it charges. i'll also get it tested with a multimeter.

it could still be that something is intrinsically wrong with the battery and it can't hold a proper charge and the alternator is good....or the alternator is crapping out and can't fully charge the battery. i still don't know.

slemmer 03-25-2010 11:14 PM

Did you say you had the battery checked? Check the electrolyte levels unless its a gel bat. I'm red flagging their comment that the battery test revealed a low CCA result. Did you have a chance to fully charge the battery with a charger afterwards? What was the voltage reading with the car running? If it's on the high side then I definitely would check the battery fluid levels.

doogee 03-26-2010 01:19 AM

Sounds like either you have something draining the battery overtime, or it's time for a new Alternator. A 30 min drive should charge it.

But there is also the possibility the battery is toast. Tough call.

pawcio 03-26-2010 07:43 AM

while running the voltage should be 14V.
if the alternator is bad it would be lower, but what about if the battery is bad. will a 'dead' battery still read 14V while running? would that be the final test to decide between battery and alternator? or is a crappy battery still going to read under 14V while running?

dbworld4k 03-26-2010 07:44 AM

I had similar symptoms last Fall, ended up replacing both the Alternator and Battery...

pawcio 03-26-2010 12:27 PM


Originally Posted by dbworld4k (Post 1403895)
I had similar symptoms last Fall, ended up replacing both the Alternator and Battery...

i hope that's not the case. my new plan is to get the battery fully charged, measure it it a multimeter, place it back in the car, start the car...hopefully read 14V at the terminals, which would determine whether the charging system is ok. turn off the car and monitor the voltage over time while the car is off with a mutlimeter. a member of another forum told me that a relay in his car was faulty, which resulted in power being drawn from his battery when the car was off, eventually discharging it.

any other suggestions or confirmation of my plan would be appreciated. thanks.

pawcio 03-26-2010 06:55 PM


bimmersport is the best...enough said.

jabela 06-06-2013 04:03 PM

So what did bimmersport do to fix it?

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