Well Merry Christmas to me :rolleyes

I'm trying to figure out if I have a bad battery or alternator. My battery is only at about 9 volts when the car is running. Is the following an accurate test?

Car running disconnect the positive battery post and the car immediately dies - bad alternator??

Happy New Year!

yup, exactly what that means. that is the old school test for an alternator or generator

yep alternator is buggered.

Okeedokee

Thanks for the clarification. I'll be taking the alt out tomorrow and going for the rebuild.

Rob

with the car running and your multimeter hooked up to the battery, you should be gettin around 13.8v ~ 14v

Chances are it's just the brushes on the back of the alternator. You can just pull them out and see how toasted they are. Pretty cheap to replace and pretty simple too, but much easier to replace with the alt out of the car, because you'll have to do some soldering.

Chances are it's just the brushes on the back of the alternator. You can just pull them out and see how toasted they are. Pretty cheap to replace and pretty simple too, but much easier to replace with the alt out of the car, because you'll have to do some soldering.

I'm going to take out the alt tomorrow morning for a look. I'll check the brushes. There's also a good place in town that fixes alts and starters that I might go to as well.

I'll let you know how it goes.

Rob

depending on how long your system has been running like this, you may be up for a new battery aswell. Sitting flat is the battery's worst enemy. and technically, anything below 12.4v is a flat battery.

depending on how long your system has been running like this, you may be up for a new battery aswell. Sitting flat is the battery's worst enemy. and technically, anything below 12.4v is a flat battery.

The battery has been on trickle charge overnight. I'm pulling the alt today and we'll see from there.

so the alt joint was finally opened again today. I took my alt in and it bench tested 100%

The first thing out of the guys mouth was "wow, that pulley sure is shiny". :rolleyes

OK, so maybe I am a dumb-ass, maybe the belt wasn't tight enough - I'm not above that.

But here's the thing, with the alternator hooked up, removing the negative cable on the battery killed the car immediately and the belt wasn't slipping.

Is there some sort of regulator in the system that could be going sideways?

When you removed the alt, was the ground wire to it intact? And the grond from the engine to the frame? You may need to clean those, clean the battery ground, etc. Was the charge light on? Does the light work?

Voltage regulators can give intermitten problems, The one in my e34 did, it took a year to finally figure out why the battery kept dieing. Try your tests again but run the RPMs up to about 1500. On my E21 the alternator doesn't charge until I think 1200RPMs.

When you removed the alt, was the ground wire to it intact? And the grond from the engine to the frame? You may need to clean those, clean the battery ground, etc. Was the charge light on? Does the light work?

There are two wires going to the alt. Positive is the one with the rubber cover and neg is the on the wire with plugs in. I did notice a brown wire with an eyelet connectection that comes off of the ground wire on the engine/frame ground. This is not the same as the ground wire that goes to the alternator though.

I will be reinstalling a little later today and testing. Before I took the alternator out we noticed that at idle the battery was about 9.85 volts.

Voltage regulators can give intermitten problems, The one in my e34 did, it took a year to finally figure out why the battery kept dieing. Try your tests again but run the RPMs up to about 1500. On my E21 the alternator doesn't charge until I think 1200RPMs.

Is there a test for the regulator and where is the regulator?

The regulator and brushes are one assembly on the back of the alternator.

There are two wires going to the alt. Positive is the one with the rubber cover and neg is the on the wire with plugs in. I did notice a brown wire with an eyelet connectection that comes off of the ground wire on the engine/frame ground. This is not the same as the ground wire that goes to the alternator though.

WRONG! There's your problem. The brown wire from the ground strap is the one and only alternator ground. The small wire that plugs in is the exciter. It absolutly cannot work with the brown wire disconnected (mounted in rubber bushings remember).

WRONG! There's your problem. The brown wire from the ground strap is the one and only alternator ground. The small wire that plugs in is the exciter. It absolutly cannot work with the brown wire disconnected (mounted in rubber bushings remember).

that makes total sence but where does it attach?? There are two studs on the alt, one connects to the wire with the rubber protective cover and the other other stud on the edge has never been undone. As as if the negativer wire was never connected to alternator in the first place.

I would take a picture of the damn alternator but I lost my dig cam on New Years :rolleyes

that makes total sence but where does it attach?? There are two studs on the alt, one connects to the wire with the rubber protective cover and the other other stud on the edge has never been undone. As as if the negativer wire was never connected to alternator in the first place.

I would take a picture of the damn alternator but I lost my dig cam on New Years :rolleyes

Wait a sec - does the brown ground and the wire with the rubber protector go on the same stud by chance?????

Nooo! There is a stud on the frame of the alt near the edge where it goes. It's just on the case, doesn't go through to anything inside. Brown and red wires never go on the same stud!

I have the bad luck to have a good alternator and good battery but bad alternator bearings. :( I may opt for the e30 alternator upgrade.

Nooo! There is a stud on the frame of the alt near the edge where it goes. It's just on the case, doesn't go through to anything inside. Brown and red wires never go on the same stud!

FOR GOD SAKE, DON'T HIT ME!!!! :lol

I wouldn't do that - it was only a question - maybe not a good one but just a question.

There is one bolt on the edgeof the case that does not have a nut on it, having said that, it doesn't look like it ever had a nut on it where the other case bolt does have a nut. Anyway, the good thing is that I know where the ground goes now and I'll be getting my hands dirty shortly.

So that does that. I know understand where the confusion was. There were actually two wires attached to the ground strap for the engine (courtesy of a PO I'm sure).

The brown wire at the top of the strap was not used. It was the "red" wire at the bottom of the strap that had a broken eyelet and guess what, when I took the nut off of negative post on the alternator I found the other piece of the eyelet :rolleyes. So that's a pretty easy fix.

Everything is back together and purring like a kitten. The Alternator that I have is an aftermarket Napa. It was pointed out to me that it has a "b class" pulley on it and the pulley on the fan is an "A class". This explains why my belt is sitting to far into the pulley and makes a squealing sound. Has anyone else heard of this issue or had this problem with aftermarket alternators?

Also, thanks again to Fullswing for graciously sending me new bushings for my alternator - it definitely made a difference!

Rob