Another Charging Question. Apologies

[M10Fan]

I’m hoping this is brief and kind of straightforward….

‘76 02, carb, not tii. Charging system problem. 
L light comes on dim once car starts and idles. With throttle, it brightens and the volt gauge goes well past 12 up to 14-16. Very linear relationship between throttle, L light brightness, and volt gauge. 
I followed the very nice article on troubleshooting of the charging system.
The battery is right at 12.6V.

The alternator at 1300 rpms with the lights and blower on reads 12.3V. 

I performed the regulator bypass with the wire bridge and this had no effect on the aforementioned symptoms. 
I futzed around with the alternator ground and actually moved the distal end to a bolt on the engine block that I believe is the intended - though not original to me - location. 
I am fairly certain based on all this and the sub 14V at the alternator that the alternator is the culprit. I have included 2 pics to hopefully rule out any other issues. 
the first is the location of the ground wire - is this acceptable?

The second is the female alternator plug looking pretty ratty. Does this need replacement before the alternator? My feeling is that if the issue was only a crusty old plug, the symptoms would be less consistently reproducible. 
Am I on the right track? As always, all the help here is greatly appreciated. 

[John76]

The ground wire in your picture is connected to the air-pump diverter valve mounting plate. This is not a solid ground point for a 45A alternator. The metal plate is bolted to an aluminum casting that has a gasket between it and the iron engine block....creating too many opportunities for corrosion and high resistance.

The ground cable from the alternator body should be the same wire gauge as the red wire going to the battery. Connect it to the engine block directly. The rear alternator mounting bracket bolt is ideal.

 

Clean and check the wires and 3-prong plugs on the alternator (D+ blue, D- brown, and DF white). They look "tired".

 

Your symptoms indicate a bad/stuck voltage regulator. Replace this after cleaning up the ground and connectors.

If this doesn't help, then check the diodes and/or rebuild the alternator.

 

John

 

[Mark92131]

2 minutes ago, John76 said:

They look "tired"

 

I would agree.  After cleaning with electrical contact cleaner, see if you can use a needle nose pliers to re-crimp the 3 connectors for a better fit on the alternator.

 

Mark92131

[M10Fan]

Thanks John. I will move the ground. 

I have actually already tried a new regulator since it was such an easy and inexpensive option. No dice. Symptoms unchanged.

[Conserv]

As John suggested, a charging light that glows dimly at idle but brightens with revs can certainly be caused by a faulty diode.

 

If better grounding doesn’t solve the problem and the issue appeared to arise overnight, I’d take my alternator to the alternator guy and have him check it, explaining the symptoms

 

Regards,

 

Steve

 

[Stevenc22]

Faulty diode. Just had my alternator rebuilt because of the same problem. L light glowing brighter as you rev up and voltage too high. 

[Stevenc22]

Advise from Son of Marty on my thread about my alternator. 

 

Measure the alternator output using a multimeter set in AC mode. It should between 50mv and 100mv. If it's much higher than that the diodes are dead and back feeding. Mine read 250mv when my diodes were dead. 

[M10Fan]

Oh that’s an interesting idea. Regarding the test in AC mode with a multimeter: should this be performed in the same manner as the alternator test in the FAQ article? With the motor > 1000rpm, headlights and blower on?

[Son of Marty]

You can measure it at idle, no need to put a load on it, IE headlights and blower.

[tech71]

WTH is that piece of plumbers strap supposed to be doing?

Even if it  is a bad diode your grounds need attention

[M10Fan]

🤷🏻‍♂️ taking things one step at a time. 

[2002iii]

43 minutes ago, tech71 said:

WTH is that piece of plumbers strap supposed to be doing?

Looks like it's holding the dipstick tube in place.

[Rich]

I was having similar problems chasing down an alternator ground and I called the Hack Mechanic, Rob Siegal, and he walked me through the trouble shooting over the phone, ( thanks Rob ) and here is a link to an article that he wrote and sent to me, I hope it helps, again all the credit on this article goes to Rob, 

 

Richard, here's a short piece about charging system basics. It includes a link to another piece about the alternator warning light, as well as the procedure to "full-field" the alternator.

https://www.bmwcca.org/roundel/bmw-2002-charging-system-diagnostics