2003 bmw alternator giving 14volt no charge to battery

a bad battery would give a wrong judgement of an alternator output. take off your battery and replace with a working one, test your alternator output using a DMM it should read about 12.5 when engine off and 14v when engine start running any figure more or less shows you have a bad alternator or an incorrect input current to the alternator....hope this fixxx it?

Several things need to be checked before an accurate diagnosis can be made, however in general it is most likely your alternator going out OR a bad connection in your alternator/charging circuit wiring.

It's also important to test/verify that you have a good fully charged battery (with no dead cells) before any tests of the charging system. An alternator needs ample battery power into it before it can produce good charging voltage and amps out of it and back into the battery.

If you test the voltage directly out of the alternator's output post/connector (with the output wire disconnected), you will be reading direct alternator voltage output, which should be approx 13.5 to 14 volts, steady. If the voltage is at ~14 volts, then suddenly cycles down to 9 volts (or anything less than 12 volts), then you have a defective alternator.
If the alternator, while isolated, tests out at a constant 13.5 to 14 volts, then the problem is most likely a bad wire or connection in the charging circuit wiring.

There is also the possibility of the battery (how old is it?) shorting out internally, causing the voltage fluctuation. That's why I previously said you need to verify each battery cell is fully charged and good. You can usually test this with a battery hydrometer (if it's not a "sealed" maintenance free battery).

Suing a volt meter check to see what the charging voltage is at the battery with the engine running. If you see more than 14 volts than the alternator is working. If you see less than 13 and most likely you will see 12, the alternator is not working. Next shut off the engine and make sure there is 12 volts on the large cable/terminal on the back of the alternator. If there is replace the alternator.

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You need to run tests to diagnose. Your battery may be junk or your alternator may be over charging. I think, from your symptoms that you need a battery. Pull the battery out and bring it to a parts store. Call first to make sure they provide that type of service. Batteries are good for around five years. They can become defective in different ways. One way is that the soldered bridges break and instead of your alternator charging a 12.6volt battery, it now is over charging a 10.5volt battery. So have the battery checked, make sure all the connections are clean and tight, and then checking the charging system. The alternator should be maintaining a 14volt current to the battery. Let me know how your repair went, good luck.

Brother Mark, changing the battery with a new one being done won't make the light go out, as you noticed. Light is still on so you changed the alternator. Good, but the battery light is STILL on. This only means that the charging circuit from the alternator is not working in the voltage regulator or the wiring is not connected properly to the alternator/regulator. A new battery will show over 13 to 13.5 volts not connected. An old battery will still show 12 volts and still be weak or bad. After connected and engine running, the system will show at least 14 volts because alternator/regulator is working properly, using a voltmeter/load tester connected to the battery. If after replacing the battery and alternator it is still reading 12 to 13.5 volts, it is not working and the light will stay lit on the dash. You may have purchased a faulty alternator if the system tests out this way. Have your system checked with a volt meter or load tester bit be sure all the connections are proper and clean.

You definitely have a problem with the charging system. As it is, the engine and other electricals are running your battery down. You need to put a voltmeter on the battery with the engine running to verify no charging. When the alternator is working and charging, the voltage will be about 14 volts, or somewhere between 13.5 volts and 14.5 volts. It may not even crank the engine over fast enough to start if your battery voltage is now under 12 volts. Then you would need a boost, but if alternator is not working, what charge you now have in your battery may be quickly depleted and the engine will shut down.
Test the alternator as I stated, or take it off and have it tested at a parts store.

Sounds like a bad alternator. Drained your battery and when you turned on the lights it took all the power left in your battery. When you drain a battery down that far, they are real hard to jump, and coupled with the alternator, the car is not producing enough current to start and stay running.

I would take the alternator off and take it to oyur local auto parts store to be tested. If bad, replace it and charge the battery fully before starting. Then check voltage at battery with motor running. Should be 13.2 -14 Volts DC. If not, you may have a bad battery cable or blown fusible link. (especially that if the alternator tests good).....Mike

hi well this looks like the battery is flat, either something has drained it, ie, partly open door (interior light) , boot light not going out, something left on lights? anything like that can cause this to happen, the other thing it might be is that your alternator is not charging the battery, you could get a jump start and get the alternator tested with a volt meter, if it reads less than 13volts on idle it is not charging , if it reads 13 volts on 1000 rpm, its not charging either. it should be 14 to 14.5volts anything over that to means the alternator is u/s as over charging the battery could cause just as much problems as not charging it correctly...hope this helps

alternator has likely failed. Check voltage at battery with engine running. Should be at least 14 volts. If you don't have voltmeter, remove alternator and take to parts store for testing.

check your battery cable connections. Remove cables from post, clean with post cleaner, $3 at Kmart, Sears, auto store.
If that is not it, have auto store test battery (for free) after you charge battery. You could have a shorted cell in the battery.
Check to see if battery is being charged by alternator this way:

• Test battery voltage with volt meter. It should read about 12 1/2 volts. (Engine off).
• Test battery with engine running. It should read about 14 volts if the alternator is putting out.

Hopefully it's just dirty battery connections.

If this solves your problem, please rate as fixya. And, good luck. Report back results.