Alternator not charging battery..HELP!

[tfritz]

First off, this is on my m30 swapped car. Alternator checked out okay at the parts store and ran between 13-14 amps. With the car running I am only getting 11-12 volts at the battery.

-The battery light on the dash does come on.
-With the car running, voltmeter hooked to battery +, and hooked to small post on alternator I get a reading of 10 volts. Is that low?
-When voltmeter is hooked to large post I get a reading of 12 volts

Any input would really be appreciated. I am having withdraws from driving this thing!! :(

[daytonaviolet]

what happens when you disconnect the GND of the battery when the car is running? does the car die?

[tfritz]

^Yes, car dies..

[daytonaviolet]

the alternator should be able to power the car even with the battery low or dead. i believe your alternator is bad.

[tfritz]

The alternator did check out okay but I did read somewhere that the diodes in the alternator can slowly crap out one by one cause the alternator to check out okay on a machine, but not put out enough when under load. Just want other input before I dump $200 on a new alternator.

Thanks for your input daytonaviolet! Still looking for more tho!

[TurboJake]

13-14 amps is nowhere near enough to run the car.... The M30B24 alternator is rated at 90 amps, and the B35 is rated at 115.

I do hope you mean between 13 and 14 volts.

[MF DOOM]

Just had this issue. Try adding a ground wire (i used 4g) and go from the alt. to the chassis

[Gregs///M]

Yes, check your Engine ground cable. This closes the ground loop from the starter, alternator, and many other engine electronics.

[tfritz]

Sorry, Yes i did mean volts, not amps!

MF DOOM, Where on the alternator did you attach the ground cable?

[tfritz]

I ran a ground cable from a small post on the alternator case to the chassis ground post and this did not solve the problem. Is there somewhere else I should attach the cable on the alternator before I try a new alternator??

[tfritz]

Just installed brand new alternator AND ground strap. Still only 12 volts at battery!!:curse:

[tfritz]

dont worry guys..im a dumbass, i figured it out

had wire to starter on wrong post..:oops:

[daytonaviolet]

so.. is the battery light still on with new alternator?

[Gregs///M]

so.. is the battery light still on with new alternator?

Welcome to the forum Daytona, didnt know you were in the E30 scene. I'm Gmannino from M3forum btw.

[daytonaviolet]

Welcome to the forum Daytona, didnt know you were in the E30 scene. I'm Gmannino from M3forum btw.

wassup man. i had an e30 before i had my 95' daytona violet m3. sold it years ago, but alot of my friends have 91 e325's. so i do alot of installs on them now :)

i have this urge to get like an AW '91 vert. then add the m-tech 2 kit with some RS's. .. but perhaps im just dreaming :)