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#1 (permalink) Old 03-03-2006, 09:52 PM
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alternator or battery

hi guys.
please help me out here. long story short. i think i need new alternator but im not sure if its the alternator or the battery. some body told me how to check the alternator .which is , when the engine is runing, take out the wires from the battery after that if the engine stops, then it means alternator is bad,or if engine is still running then it means battery is bad.

and one more thing. is it easy to change alternator? and if some body can post some pics about how to change the alternator. i will appriciate that.

i thinking of getting 140 amps alternator. i have 325i 94 . i hope it will fit in. because factory one is 80amps.

thnx alot
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#2 (permalink) Old 03-03-2006, 10:05 PM
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Digital multimeter....

Moe use a digital multimeter and read the voltage off the battery terminals when the engine is running. If it's 13-14 volts then the alternator is good. What's it doing? If the battery is more than 4 years old don't be surprised if the battery is bad.





Mike
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#3 (permalink) Old 03-03-2006, 11:37 PM
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Don't remove the cables with the car running. May have worked in the old days, but you could zap the ECU these days, big bucks to replace. LIke Ham said, use a multimeter. Are you planning a lot of audio upgrades? The 80 amp does just fine unless you are really loading the car with amps, screens, etc.

1995 325I, window tint, K&N, debaffled airbox, BMW #104 wheels, Nighthawk low beams, smoked side markers, smoked corners, smoked taillights, M3 stlye heated mirrors, various interior bits, Bosal cat-back.
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#4 (permalink) Old 03-04-2006, 04:40 PM
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Just take both out of the car and have each checked out at Autozone or some other auto parts store. Keep in mind that the alternator may pass the bench test even if the voltage regulator is bad. In this case, I would suggest that you change out the entire alternator because the alternator cannot be too far from failing if the voltage regulator is already bad.

Changing the alternator is pretty straightforward. You will need socket wrenches (I believe 13mm, 10mm, and 17mm).

- Disconnect the negative battery cable
- Remove the alternator cooling duct and the air filter housing from the car.
- Disconnect the wiring from teh alternator (two nuts: B+ and D+)
- Remove the alternator drive belt: you need to release the belt tensioner using a 17mm socket and turning it clockwise.
- Once the belt is out of the way, remove the two bolts that hold the alternator in place (17mm I think). Make sure to keep track where each of the two bolts was, since one is shorter than the other.
- Installation is reverse of removal.

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#5 (permalink) Old 03-04-2006, 05:33 PM
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what's the symptoms? when you turn the key over (not turn the car on, just turn the key over) do your internal lights/radio/etc. turn on? are they dim or do they fully light up? when you crank the key over to actually turn on the car, does a repetitive clicking noise occur?

before you go replacing anything, check the battery posts. if it's been a while there may be some carbon buildup (it'll be green and kinda crusty). make sure there's none of that gunk on there. if you have to, disconnect both posts on the battery and take a 1000-grit (lol, that may be wrong, it's been a while) piece of sandpaper and lightly run it through the connectors (not the battery posts, but the cable connectors) until it's nice and shiny and gunk free. this will ensure a good contact point for the battery posts.

there's no need to spend bookoo bucks if it's something simple and easy to fix.

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#6 (permalink) Old 03-06-2006, 03:59 PM
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Definitely DO NOT remove the battery cables with the engine running. Use a multimeter to check if the alternator is putting out 13-14V will the engine is running. You can check that by touching the power post at the fuse box with the positive lead from the multimeter and a touch the negative (ground) lead to the case of the alternator. You can also remove your battery and take it into Autozone or Pepboys and have the battery "load" tested.

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#7 (permalink) Old 03-06-2006, 04:01 PM
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Dont remove the cables form the battery with the engine running. Bad.

Do the above checks for the alternator... or get someone else to do it... probably a bad battery.

Les


1997 E36 M3 1990 E30 325i
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