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Car wont start sometimes

(2003 BMW 530i)
in Bremerton, WA on June 17, 2009
About 4 months ago I started having problem with my BMW not starting up whe I come out in the morning or after work or somethong like that. I thought It was a low cell in my battery or the life of the battery. Everytime this happens I gety a jump for the battery and it starts right away and holds the charge for a few weeks infact, then the process starts all over again after the few weeks. I decided to buy a new battery a few weeks back and everything seemd to be ok, I was also told that if could be a eletrical timing inside the altenator that is going bad or somethng like that. Anyway yesterday I went to start my car up and It started agin with not starting and needing a jump. I've checked all my compenents on my car and I do not see anything that is running down my battery, I have no special stereos, dvd players fuses or nothing of a sort. I have a yellow wire attached to my + battery terminal and found out that belonged to the air bag detector for the passenger side. And also there is a thick red wire attached to the + terminal as well, but not sure were it leads all of these cant be drawing bad power from the battery because it was manufactured like that. No lights or left on inside or out I check this out all the time and just a bit of more info my check engine light came on before this started happening and I went to Auto Zone and they plugged up their machine and said that it was an emissions code. So I guess I did not clsoe the gas cap tight enough. By anyhow I do not think they are related in anyway even though I started experienceing these starting issues soon after. Hopefully someone out there has had these type of problems with their BMW, I've researched this problem on the internet and I've seen tons of possible causes but I need a close to definite answer so I'm not spending thousands of dollars running a simple problem down. If anyone can help and has a clue please let me know I struggling over here to know why this is happening.

Displaying 3 answers & 1 comment
Popular Answer
on June 18, 2009
I've chased a few of these before (other European brands) and they are really tough because of the intermittent nature of the problem. It is very important to try and remember exactly what electrical devices you used the night before (Heater, Radio, A/C, opened the trunk etc.). Write down how far you drove, the outside temperature, and anything else you can think of. after a couple times you migh see a trend.
You can also try checking the amperage draw on the battery and if it is found to be too high, you can try and locate the source of the draw by pulling fuses to isolate the circuit that is causing the problem. I've seen control relays stick and cause this type of problem, as well as blower fan control modules.
Hope someone with BMW experience can jump in on this one!
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on June 18, 2009
Thanks Bret I will definitly test out those things. I've been tols about the fan blower module as well so thats another thing to look into. Also after reading the post from the gentleman about the 01 BMW that he was having the same issues as me Im kind of convinced that Im having altenator issues as well, so I will be going all these routes to look into thanks again.
on August 10, 2010
I have had this problem. Took it into the shop 4 times and they couldn't find anything (one of the times it went in on the tow truck). It was not the battery or any issues of electrical draw, not the alternator, not the fuel pump, etc .... They put their best guy on it and it became a mission for him ... but he never found anything. So .... I had them do an Inspection I service early and also replace the spark plugs .... and voila .. no issues for a year now. A tune up did the trick.
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on January 11, 2011
Do you have the correct battery? Battery spec. 90AH, 160RC AND 720CCA
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