Sorry another charging problems thread

[iPee]

I know there's one from Stonea, I have a feeling it may be a similar issue, but wasn't sure. Also didn't want to thread jack.

I started noticing an issue when I was stuck in traffic couple times and the stereo would start cutting in and out and lights start to flicker. I didn't pay too much attention to it. I was hoping it would go away haha. Then one night I warmed up the car in the garage and the car would show these same signs couple mins in. I took out the dmm and it measured 11.8V at idle.

Thought it was the voltage regulator at first, so took it out and the brushes were indeed worn down. Replaced the regulator with a new one, and tested for voltage at idle 11.8V again.



Next I noticed that the battery light wouldn't light up with the key to the ON position. So I swapped the light with the oil light which I know works for sure. Turn the key and it is still the same, the battery light stays off and the oil light will turn on. This leads me to believe the bulb is not burnt.


I've read that older cars if the bulb was burnt it would prevent the alternator from charging. I have a 91 318IS which is a newer car and should have a resistor wired, but as you can see there is no resistor on the circuit board. Also the light bulb shouldn't be burnt as noted from above test. It's also a Canadian car not sure if that makes any difference.



So I went back and checked the alternator and noticed the blue wire is loose. Tugged at it a little and it came right out. I thought oh this must be it, so i extended the wire and put a new ring terminal on it. Tried the voltage at idle again and still only 11.8V.

So is the alternator at fault here or are there other things I should test for as well?

Idle 11.8V
2000rpm 12.8V
New voltage regulator
Battery replaced last October
Load test on battery: good
New SI board: Bavresto
Lukebox $500 stereo setup

[uturn]

The slip rings.... is it grooved where the brushes wore them down? Yes? Time for a new alternator.

[iPee]

Thanks for the suggestion. I'm assuming I'll need to disassemble the alternator to see the slip rings or will the slot where the voltage regulator goes into be big enough for me to check it?

[uturn]

The brushes on the voltage regulator rides on the slip rings. You can see them in the opening. Looking at your old brushes I'm sure you have a deep groove cut into them. Your dmm readings shows that your wiring is good because at 2000rpm you got an increase in your voltage output meaning power is getting from your dash to the alternator to energize the field. Be sure to buy an OEM Bosch rebuilt alternator. Anything less will likely leave you crying.

[uturn]

Also recharge you battery... you don't want to overwork your new alternator and burn it out.

[Cephas]

Seems like you are getting some charge since rhe viltage increases at the higher rpm's. Sounds like something on the alternator itself has burned out.

For fun, what voltage do you get at the D+ wire (the one you repaired)?

[iPee]

I'll have to plug the dash back in to test this properly right? Also how do I measure this, I'm a noob when it comes to electronics. Take one prob and touch the D+ wire and where do I touch the other probe to?

[iPee]

So I tested the voltage at the D+ terminal and touched it to the plate at the back and it read 11.5V and the battery was reading 11.75V with the key in the on position. The battery reads 12.38V with the key in the off position.

[iPee]

So the D+ terminal reads about the same voltage as the battery with the key in the on position but how come the battery light doesn't light up?

I also wanted to confirm that the thicker black wire here on the starter connects to the B+ terminal on the alternator. I plan on ordering the ground kit from bavrestoration so just needed to confirm this is the right one to replace.


The ground wire doesn't look to be in the best condition either so I'll be replacing that as well.


I also noticed there is no engine to chassis ground. I read that it connects to driver side frame rail or motor mount to oil pan. You can see that there's no ground wire here unless I'm looking at the wrong spot.


Lastly here is the picture of the slip ring.

[Cephas]

Yikes. Get those grounds sorted out and see if that helps. No engine ground could cause some very strange issues.

[iPee]

Anyways going to order a Bosch Alternator and hope that fixes the issue. Uturn's been helping me out a ton so once again thanks for that.

Cephas I found the engine ground. For anyone thats wondering it's on the passenger side frame rail and connects to the passenger side motor mount. This is for a 91 E30 318is, I think for the other trims it's usually driver side frame rail to oil pan.

[Cephas]

Makes sense on the ground. Forgot that you're in a 318. End of the day, I think alternator will do it for this one. You're getting the right voltage at the D+ wire, so the exciter is telling the alternator to send a charge out. The alternator just isn't up to snuff.

[iPee]

Finally got around to doing this today, got some good news and bad news. The good news is the battery light turns on now when the key is in the on position, however the car can't maintain it's idle. Once I let go of the throttle the car dies immediately. Also coolant was leaking out like mad.

I replaced the ground wire pictured here with one from Bavarian Restoration. However the ring terminals from Bav were too wide to fit into the original position. So I used the bolt right above it. Is this fine or must I use the original location. They both go on the same plate so I assume it's fine.


The only other reason I can think of the car not idling is I have a vacuum leak somewhere. Prior to the ground kit and alternator arriving I took apart the intake manifold to see how the starter to alternator was wired because it goes through a harness box right underneath the manifold. I think I must of cracked some vacuum lines and coolant lines in the process and didn't really notice when I put everything back together. I guess the next logical step for me would be to tackle the mess underneath the intake manifold.

[AndrewBird]

Doesn't matter what bolt the ground is connected to.

And yes, vacuum leak is likely your source of the idle problem.