Doesn't run after new alternator install

[Kyle in NO]

Well, there you go.

[cjthemountain]

Well, there you go.

Umm, busted alternator? Missing ground cable? Both?

[cjthemountain]

These directions add to my confusion. They came with the alternator. I pulled a version 2 alternator out of my car, and it had the supression capacitor on it. The above directions only show a supression capacitor on version 1.

If my car had a version 2 alternator in it and no blue ground wire, why was it working fine since I bought it?

Should I remove the suppression capacitor?

I guess I'll pull the alternator and have it tested tomorrow, and try to pick up an extra cable to ground the alternator properly. I still don't know whether or not to leave the suppression capacitor on there...

Can someone post a pic or describe how the alternator should be grounded? Can I just run a cable to where the battery's "-" side grounds to the chassis or does it need to go to the ground location atop the header?

EDIT

I found some loose electrical wire in my closet. Stripped the ends and grounded the alternator casing to the engine block. Voila - battery light now turns on when the key is in the on position. It turns back off when i start the car. I'm getting 12.5v at idle (still) between ground and diagnostic pin 12, and holding a couple thousand RPM doesn't seem to increase the voltage.

I should be getting more like 14v at idle? Or at least when I give it some gas? The ground cable I just added might have too high a resistance... or the alternator is in fact bad. I will try to check both tomorrow.

Here's the old alternator - clearly (ish) floating on bushings. A discerning eye will notice the shiney metal on the post up front. I pulled that nut off so I could ground the new alternator casing. It was the first time that nut ever came off, so yeah, the old alternator's case was never grounded as far as I can tell. And it never gave me trouble until recently... weird. Maybe the very dilapidated bushings were allowing a ground through the mounting bolts? Those bushing were completely mush.



This still begs the question, if the car was supposed to have a separate wire to pull the motor casing to ground, where the hell is that wire? I can't find it. Or could it be that my car HAD the older(?) style alternator that grounded through the mounting bolts, the last owner put a new alternator in (the one I pulled out) and got lucky somehow?

the new alternator has a bent post, which means it was probably dropped at some point on it's way to me so I'm feeling way less confident it's working correctly

[Kyle in NO]

Grounding the alternator body has basically solved your problem by completing the circuit. I'd return the alternator and request one with solid mounts, for an '88 528e.

What year and model is your automobile?

[cjthemountain]

I've got a 1985 535i, production month was January. WIll the one you suggested direct fit?

[Kyle in NO]

Yes, but order one for an '87 535i instead.

[tn535i]

I found some loose electrical wire in my closet. Stripped the ends and grounded the alternator casing to the engine block. Voila - battery light now turns on when the key is in the on position. It turns back off when i start the car. I'm getting 12.5v at idle (still) between ground and diagnostic pin 12, and holding a couple thousand RPM doesn't seem to increase the voltage.

I should be getting more like 14v at idle? Or at least when I give it some gas? The ground cable I just added might have too high a resistance... or the alternator is in fact bad. I will try to check both tomorrow.

First, Sorry if I remembered it wrongly but appears the blue wire also has a lug you screw into place not a clip. But you clearly have the situation figured out... There are two wires there as the other goes to the diagnostic.

So about checking at pin 12 on the diagnostic and getting 12.5v, I wonder if that might be misleading. There could be some voltage drop or the battery is still charging. I would measure the big red wire or (with a good ground to the alternator) just put your meter on the battery terminals. If you get >12v with the engine off your battery is more or less 'charged' and once you start the car you should get close to 14v but I find my old BMW's generally setting about 13.8v with engine running and little load. Then add some load like lights and fan and it should not change but a little maybe a slight drop and may even kick up just a bit.

The bent stud would not bother me too much if the alternator checks out and works well. Maybe not worth the trouble of pulling it again. But realize if you add a ground strap it needs to be about the same size wire as the red one to the battery since it flows essentially the same level of current. Your alternator is moving current from (-) to (+) not creating electrons from nowhere which is why you need a good ground.

[cjthemountain]

I'm not getting anything over 12.5v across the battery terminals with the car running. could be the alternator, could be the shitty ground. I just called autozone and ordered the '87 535i alternator which I've confirmed with the autozone guy DOES NOT have the the bushings - it's a direct metal contact mount. And they're letting me exchange the one I already bought, so I don't have to pay extra That should solve the grounding issue, and I'll have them bench test the alternator before I leave the store. Hell, i'm going to install the damn alternator in their parking lot.

SO, that should solve any alternator issues I'm having. I may or may not still have a short somewhere in the system. I'll be checking that soon too. Can I just check across the fuses for any current that shouldn't be there when the key is in the off position?

[tn535i]

If you are new to a DMM be wary of checking for current vs voltage or things might go pop, hopefully just the fuse in the meter. Voltage you can usually do no harm but mistakes in the way you measure current can lead to bad things. Just be cautious and make sure you know what you are doing first. And don't for example try to measure the current output of the alternator, I doubt your meter can a handle that. However, it is great for checking the current draw on the battery with ignition off or fuel pumps once running.

You can easily check all your fuses for VOLTAGE with the key both off and on without possibility of something going pop. This should help confirm if you have power where you should but some fuses have constant power and others are switched so you might need to compare to the ETM.

What are you looking for or suspicious of ?

[cjthemountain]

If you are new to a DMM be wary of checking for current vs voltage or things might go pop, hopefully just the fuse in the meter. Voltage you can usually do no harm but mistakes in the way you measure current can lead to bad things. Just be cautious and make sure you know what you are doing first. And don't for example try to measure the current output of the alternator, I doubt your meter can a handle that. However, it is great for checking the current draw on the battery with ignition off or fuel pumps once running.

You can easily check all your fuses for VOLTAGE with the key both off and on without possibility of something going pop. This should help confirm if you have power where you should but some fuses have constant power and others are switched so you might need to compare to the ETM.

What are you looking for or suspicious of ?

Well said. Yes, I am familiar with the differences in checking voltage vs. current, e.g. parallel (voltage) vs. in line (current). I figured I'd be checking the voltages across the fuses in both on and off positions, though I haven't given the ETM a close enough read through to find some kind of miracle chart where it would simply give the voltages for both key positions across each fuse. Hope such a thing exists...

[demetk]

I figured I'd be checking the voltages across the fuses in both on and off positions, though I haven't given the ETM a close enough read through to find some kind of miracle chart where it would simply give the voltages for both key positions across each fuse. Hope such a thing exists...

Power distribution pages will tell you when each fuse is powered up.

Why will you be checking voltages across the fuses? What are you going to determine?

[Mike W.]

I figured I'd be checking the voltages across the fuses in both on and off positions, though I haven't given the ETM a close enough read through to find some kind of miracle chart where it would simply give the voltages for both key positions across each fuse. Hope such a thing exists...

Power distribution pages will tell you when each fuse is powered up.

Why will you be checking voltages across the fuses? What are you going to determine?

Checking for current across the fuses is a great troubleshooting tool. Voltage no. Remove the fuse and hook the leads up to either side to read current.

[cjthemountain]

Ok, voltage can't tell you anything useful across the fuses. Noted. I will try current after I find the pertinent pages in the etm. I'm done for the evening, it's dark and I'm hungry :p

I did manage to get my hands on an alternator for an 87 535i, it was half the cost (total bonus) and it works like a charm. With the engine running I'm getting 13.5 volts across the battery. It also happened to come with a new suppression capacitor already on it, also a bonus.

As an added test, I'm just gonna leave my battery plugged in overnight and see if it's dead in the morning. If it's dead, at least I've confirmed I still have a short somewhere.

[tn535i]

Checking for current across the fuses is a great troubleshooting tool. Voltage no. Remove the fuse and hook the leads up to either side to read current.

Agree but just be careful you don't measure a >10A current with a <10A meter. Now if we are talking about trying to find a drain with the ignition off... start at the battery and if you have more than about 50mA then move to the fuse block to see if you can find the culprit draining the battery.

[cjthemountain]

Well, with the new alternator in my battery did not die overbight, nor parked at work a full day. Everything seems fine. I'm going to check current from the battery with the key in the off position just for sanity. Do I check between the positive terminal and the positive cable, or between the negative terminal and the negative cable?

[Mike W.]

Well, with the new alternator in my battery did not die overbight, nor parked at work a full day. Everything seems fine. I'm going to check current from the battery with the key in the off position just for sanity. Do I check between the positive terminal and the positive cable, or between the negative terminal and the negative cable?

It doesn't matter. With analog meters you do have to have the cables in the right places, but with digital you'll just get a negative number.

[a]

You also gained 10 amps in output from the late model alternator. Getting the VOM is good move. New ceramic fuses, just to baseline the fuse box is a good place to start. Get a De-Oxit pen contact cleaner. rub it into the contacts and rub off when dry with a pencil eraser. Stop buying electrical parts from AZ . Never surrender your original part for the core charge until you are sure the "new" part actually works.

[cjthemountain]

so it's been a few weeks running with the new new alternator. No problems whatsoever.

Consider this solved

[Nebraska_e28]

Good to hear!

[delorean175]

Hey Guys I'm having an intermittent charging problem as well. I have 2 other issues that I think might be related. My Brake Fluid, Park Brake, and Charging light are slightly glowing and get brighter when above idle. This occurred after I changed my alternator for a re-manufactured 90A unit but the car has been running fine for 4 months this way. Also I have been noticing my tach needle bouncing around a little bit over the last 4 or 5 days but thought nothing of it until today. This started happening shortly after I installed a new TRE in tank fuel pump and deleted the exterior pump. I took special care in tying off the old wires for the exterior pump. This shouldn't really be related other than the whole fix one problem another one comes along.

Today I started my car and let it run for about 10 mins, I jumped in and noticed the headlights were really dim. Having electrical gremlins in the past I knew something was up. I turned the car off then attempted to restart and it was dead. After I recharged my battery everything seamed fine and it was charging on its own again. But I have a feeling its not a one time thing. I managed to recreate the issue one time after 10+ off/ on's. I had the lights and blower on while checking voltage while running and I did a quick off/ on and noticed the battery light was fully illuminated. I revved the engine and the battery light went back to its usual dim glow and I could hear the alternator making a whirring sound.

What I've done so far:
Checked Voltage while off 12.5v
while running 14.2v
while revving 14.2 (or 14.4, can't remember)
checked pin 12 on the diagnostic connector 14.2v while running
12. ish volts at the exciter wire while running, I forgot the exact number but a little over 12v.
while running under load with everything on High, I was getting in the mid/high 13V range.
key in the On position not running i got 1.4 ish volts at the exciter wire but goes up to 12 volts after I start it.

tested resistance between: Pin 12 on the diagnostic connector and the exciter wire on the alternator (almost no resistance)
tested resistance between: Pin 12 on the diagnostic connector and Pin 1 on the C101 connector (almost no resistance)
tested resistance between exciter wire and Pin 1 on C101 (almost no resistance)
tested resistance between alternator body and negative battery post (almost no resistance)

Battery light is working, and should have the little bypass built in as well because my cluster is from an 87.
Checked belt tension, and seams fine.

all ground should be good because 11k miles ago I put my rebuild engine in the car and made a point to clean and use battery terminal grease on the mating surfaces of the grounds (it helps prevent future corrosion).
The alternator has a ground strap and is the kind without rubber bushings (I know its redundant but why not?)

So far everything is completely normal but twice today I have had this intermittent no charge issue. I've been studying the ETM for my 1982 car and the 88 1.3 motronic wiring harness. I have an 87 Cluster. I've been cross referencing the 82 and 88 wiring diagrams for the charging circuits as well.

I'm stumped.

It seams like it only happens when It starts, meaning the alternator doesn't get excited like wants so in exchange it doesn't do anything until I give it a good rev.

I'm thinking next I will try pulling the cluster and testing resistance between the exciter wire on the alternator and maybe the other end on the C1 plug. Maybe I should make a point to juggle the wiring harness around also. I'll check the circuit board as well.

God I hate intermittent electrical issues

[cjthemountain]

this may sound dumb, but slipping belt?

[delorean175]

this may sound dumb, but slipping belt?

Its not dumb, I could see how that could throw someone through a loop. Sometimes it really is something simple. After I rebuilt my engine I could not figure out why my car wasn't getting any signal to the coil. After a few hours of testing everything I was completely stumped, Later I figured out It was a forgotten ground strap on the valve cover.

My belt tension seams to be ok. The car also hasn't acted up since the last post. However my tach needle seams to be jumping around a lot so I'm going to chase that (hopefully under dash grounding) issue and hope this was somehow related. My chassis grounds were all cleaned relatively recently.

[cjthemountain]

i had a jumping tach needle i fixed in another post... does your engine rev/cut along with the needle?

[delorean175]

i had a jumping tach needle i fixed in another post... does your engine rev/cut along with the needle?

Nope, its pretty smooth while the needle is jumping. It usually happens at 3k RPM and above. Do you have a searchable title for that thread? I would like to sort that issue out.

[cjthemountain]

For me, the RPM were dropping along with the needle. Long story short, bad wire going to the MAF (you probably have the stock AFM in there).

http://www.mye28.com/viewtopic.php?f=3&t=146580

Wire jiggle tests can go a long way