another alternator/charging light bulb question

[wolfswest]

Hi everybody,

Yes, another alternator/charging problem. I hope somebody can point me in the good direction. I’ve spent the last few hours reading many posts but I haven’t stumbled upon the same problem.

Long story short, I took my 911 SC 1983 for a road trip and it died on me: empty battery, managed to get home with a spare and started to check some things: (with the “new/spare” battery installed, the old one is charging) I noticed that my alternator light wouldn’t come on when I turned my ignition key so I took out my alternator.
I guess that was my problem before I left on the road trip: the light didn’t go on when I turned the ignition key so the alternator doesn’t charge.
I can’t tell for sure, idiot that I am didn’t pay much attention to the lights before: lesson learned.

The alternator looked fairly new (bosch replacement unit, although if it’s looking new it’s not garantueed that’s it working properly of course)
Then I checked the idiot light, and it’s working fine so the light bulb is okay. Then I’ve put the D+ (blue wire) against the ground and the light goes on, so I guess my circuit is okay.
Then I’ve put my alternator between the connections without building it back in, just a test scenario and switched the ignition key: light bulb goes on.
Okay, last night I built the engine back up, turned the key: yes, the bulb goes on, car starts, light goes out, everything seems to work okay.
Then I checked the voltages on the battery. With the car not running I get a 12.7 if I remember correctly, when the car starts it goes a little bit up to 13.2 and when I rev the car 2000RPM+ it’s about 13.5v.
So far so good I guess. Okay, took the car for a spin, stopped, started the car many times, light goes on, light goes out, okay. Then suddenly the light doesn’t come on anymore when I switch the ignition key: DAMN! I started to check some things, basicly I didn’t do anything and it worked again! Okay, I drove back home, tested the procedure a few times and everything worked as it should be. Ignition key on, light goes on, start the car, light goes out, but I worried about the one time of course!
Is my alternator broken or should I look more for a bad ground or...
Thx,

Dem

[wolfswest]

I've read some more posts and frequently there is talk about a 14 pin connector and a bad ground and connection there for the blue wire...

Where is this 14 pin connector located or is this only for models with an external VR? Mine is a 1983, so I have the internal regulator.

I also read here that I need to check the wires on my starter... Is this true or shouldn't I spend time on this?

thx,

Dem

[wolfswest]

Hi,

I just played around a bit more. My battery is now fully charged and I'm getting good numbers: car of, battery is 12,8, car starts, I get around 14 - 14,2! I turned the ignition off, tried again and the light didn't led again
Played around a bit more but this time it would work, started the car and the alternator wasn't charging, I got around 12,5 voltage...
I pulled the alternator again, cleaned the contacts of the voltage regulator, tested again and the light worked again.

I guess it's not a contact problem, every contact is sparkling clean, the alternator does his job when the light is there (at startup) so I'm guessing the valeo VR is shot.

what do you guys think?


Dem

[timmy2]

Try a new regulator, to start,cheaper than a new alt. Have alt tested by a good shop. Or reverse the order...

[wolfswest]

yeah, it's obvious it's a problem with the alternator or the VR. I hope it's the VR so I don't have to tear down the engine again...

I'll keep you guys updated,

[Joe Bob]

As I recommend in all these posts, get it rebuilt locally. Do NOT by a reman. Remans compete for lowest price fixes. You get what you pay for.



Pic of a 14 pin connector for the DME under the driver's seat. There is also one in the engine bay driver side.

[wolfswest]

Hi Joe Bob,

I already found the 14 pin connector in the engine bay yesterdag. But I guess that my problem isn't in one of the two connectors because when I put my blue wire from the alternator to the ground my light bulb works, EVERY TIME! So I guess my circuit is 100% fine. Or Am I missing something?

thx for the help and the picture, didn't know there was a connector under the seat.

Dem

[Joe Bob]

You would have a 14 pin under the seat IF you have a DME for a Motronic Fuel Injsection system found on 84 and up engines.

As to the intermittent alternator light, it could be a wonky ground. My suggestion is to somehow monitor the voltage when the glitch occurs. Spikes could be a VR, consistent low voltage when using electrical devices like lights, AC, blowers etc can be a battery that has a bad cell.

A local alternator shop can test you alt and likely do a load test on your battery. If both check out then you have a bad ground somewhere. An occurrence that is my most frustrating experience.

[wolfswest]

ah, my car is a 82 cis car...

when the light bulb doesn't light up when I turn the ignition key the alternator isn't charging. When it does, the system is running fine.

I've checked the grounds many times, every single one is looking fine.
If the light doesn't work it's always after the engine is heated up, so I guess it's the VR that sometimes doesn't work because of the heat...

The problem never occurs with a cold start, then the light operates like it should be.

[Joe Bob]

Hmm, heat.....obviously that would be something that you should mention to the alternator shop and best if the problem could be presenting itself when you went in....

Do you have a meter that you can monitor voltage while driving? Or does the alt light come on when hot and not charging?

[wolfswest]

nope, the light never went on while driving so far.

I must say I haven't driven the car much after my initial break down, just some testing and small trips around the block.

ah well, we will try again with the new ordered VR if that doesn't do the job I'm facing to let my alternator rebuild by a decent shop...

I hope to avoid this but we will see.

[wwest]

Slip ring brushes worn out or sticking, worn out would be the best bet.

Well worn slip ring brushes "travel" is limited by the wire braid connection, intermittent connection is not unusual just prior to full failure.

Miles..?

[wolfswest]

how do I recognise worn slip ring bushes? I've checked them with my fingernail and there isn't any crack or groove in them, the surface is really smooth! no oxidation either, they look like bright red copper and on the place where the brushes touch the surface is deeper red-black... the brushes are also within the tolerances.
I can post a picture if you like?

[Joe Bob]

The brush tension could be below optimal.

On the not charging when hot issue. If the light is not coming on, how do you determine loss of charging w/o a meter?

[wolfswest]

I have a multi meter so I tested the voltages I got at the battery.

with the light on before startup, I get a 14v.
when the light isn't working and I start the car I get a 12.5V even when I rev the car it stays around 12.5v...

[Joe Bob]

I would suggest one of those cheapo ciggy plugins and when it happens drag it over to the alternator shop on battery power. Hopefully it's not to far away.

I would also consider a phone consultation....

[timmy2]

Diode or regulator failing or loose solder joints that open up when hot.

[wolfswest]

Timmy,

VR is already on the way, if that's not the problem I'll take the alternator to a specialised shop in the neigbourhood. I'll let you guys know what it was!

thx for the suggestions,

Dem

[SCrescue]

FWIW, I went out for a ride last week and after about an hour of driving, the headlights and instrument panel lights suddenly went very dim. No charging light came on btw. Made it back to the house on battery power and parked it until morning. Tested battery voltage the next day, 12.5v not running, 10v at idle. Pulled the alternator and took it to a local re-build shop. Got it back a day later along with a report that the VR had gone south. re-installed it and all is good...

[wolfswest]

Hi,

I want to update this thread a bit so everybody is informed.

I received a new hüco voltage regulator a week ago, installed it and my problem is gone!
Thx everybody for the help,

Dem