Not charging- please help!!

[Conrad311]

hey guys sorry for another charging thread but im very short on free time to keep searching, and i need my car back up and running asap.
So the story is its a 87 325is, i have a new battery, car ran fine for 2 weeks after new bat was put in, and then my fuel pumps cut out on the highway from a corroded power wire in the harness and i kept cranking it till it drained the bat. then i jumped it and it hasnt charged since, ive got from 11 to 12 volts at all points, both wires coming from the alt, the power dist block, and the battery, i did some reading and thought it might be the voltage regulator due to the flickering lights when i hit the fan or stereo, so i replaced it with a oem unit, and it didnt do shit, my dash light does work, it lights up at key on and goes out after it fires up, and the car will run fine, except the lights flicker sometimes and then when i shut it off its deader than hell, the lights go dark after a matter of seconds. Im a broke college kid and i cant afford to replace the alt if i dont know its that for sure and im sick of jumping the fuckin thing.
any thoughts?
thanks alot

[White325is]

I know at my father in laws garage we have one of these.



So maybe if you go to another garage they will have one also. Might cost you 10.00 for them to check it.
I know some auto stores in town will check it for free. Maybe its the same where you live too?

[ZombiE30]

any automotive place should be able to do a basic charging test, with something resembling the tool mentioned above.

you say you replaced the voltage regulator? Because if you're getting 11 or 12 volts OUT of the alternator, that's where your problem is. It should put out 12.5-13.5 to be properly charging your battery.

[wodcutr]

If you charge your battery and you only have 12v then the battery is bogus. If the car is running you should have 13.5+ going to the battery to keep it charged!

[Conrad311]

yea but i have 11.5-12v at the battery and at the alternator, and the battery is brand new

[Disaster Inc]

If you charge your battery and you only have 12v then the battery is bogus.

^^^^^^Wrong!

One Very Simple Alternator Test:

1) Start Car and run at a normal idle.

2) Connect a Voltmeter Directly Across the battery Terminals.

3) Turn on Headlights to High Beam.

4) check the battery Voltage.
*** The Battery voltage Should read between about 13.8 to 14.2 volts. (Possibly up to 14.5 Volts.)

5) Increase motor speed to about 1500 RPM. The Alternator should now produce a battery voltage between 14.2 and 14.6
Volts.
*** If it is Lower than 14.2 volts, the Alternator probably has one or more Bad Diodes.

6) Now, Maintain the 1500 RPM and Turn off the Headlights. Run this test for One Full Minute.
"The Battery Voltage should NEVER Exceed about 14.8 Volts".
***If it Does, the Alternators Voltage Regulator is probably Faulty, OVER CHARGING the Battery.
__________________

[White325is]

^^^^^ truth...

[ZombiE30]

+1 to the above.

However, if you are indeed broke, it is possible to take the alternator apart and fix whatever is causing the problem. (Provided you have a passing familiarity with soldering irons and possibly electrical diagrams)

I'd check the integrity of the external connections and the voltage regulator first. (already did this)

Next, take the alternator out of the car, remove the big front nut and the housing nuts. It should come apart fairly easily. (remember where everything goes!)

Look for any contact area with excessive corrosion, especially the brushes. (sliding contacts that look like little steel sponges)

Next, find the diodes, and unfortunately this varies by manufacture. I am currently running a generic remanufactured one and it's arranged differently than the original. In any case, diodes are the little electrical devices that turn the alternator output AC voltage into DC (one way resistors). There should be three distinct groups of diodes, and again, this depends on how everything is arranged, you should try to test each one individually to make sure it shows resistance in only one direction.
Connect ohmmeter leads across diode, it should read very low resistance; connect them the other way, it should read infinity or OL. If it reads OL in both directions, or low resistance in both directions, it is bad and should be replaced (soldering!).

That should be enough for now....good luck!

[Conrad311]

Great help guys thanks alot, i checked the diodes and one was shorted, i was getting about 12 volts across the rpm range and it never exceeded 12.5, im pretty good with a soldering iron but for the sake of time i just got another alternator from a local scrap yard for 30 bucks with a guarantee, and to my amazement there was about 8 e30s in various states in the yard, when i get some money im going shoping :)

[wodcutr]

yea but i have 11.5-12v at the battery and at the alternator, and the battery is brand new

I have seen brand new batteries fail in one day before. Put a charger on the battery overnight and then see what the voltage is. If it is still 12v or less then your battery is bogus. If you have the car running and the alt is only putting out that much then your alt is bad. Go to the junk yard and get one off an E30 and slap it on there. Do the tests the other posters have said to do, but do them with a fully charged battery!