Alternator Exciter Issues

[cafexs]

So I've finally decided to battle my e30's charging issue, and my brain is drawing a blank at the moment. Battery's good, (both I assume) alternators I've had in the car are good.

Battery light started flickering while driving a few weeks back, and stopped coming on with the key on all together. At first I assumed my alternator kicked the can, replaced it, and charged the battery - 2 days later, dead again.

Then I started doing some research on charging business and saw that the older cars' idiot light burning out will prevent the charging system from functioning, tear the cluster apart, swap the working oil bulb with the battery bulb to test that issue, still no light.

THEN, I jumped the exciter from the alternator to the battery relay (Which I know will drain my battery if I leave it like that with the car off, it was for science, don't shoot me.) Anyways, with the exciter jumped, the battery bulb comes on in the dash, and the charging system functions, but now I'm confused. Can anyone tell me where the wire on the exciter terminal runs to physically, and maybe where the break or short may be in the circuit that's causing the problem? Since the light comes on when I send power to the alternator, the charging circuit itself would seem to be in tact if the idiot light in the dash comes on too, correct? It's just a break in the circuit from the ignition to the rest of it? My brain is numb

[jlevie]

The exciter circuit is pretty simple. The wire runs through the engine harness to C101 and from there it goes directly to the cluster.

The warning light coming on or flickering while driving sounds most like an alternator or ground problem. You don't say whether the replacement alternator was a used or rebuilt part. And if a generic reman, those are a real roll of the dice. You may have to go through two or more to get one that works. I only use genuine Bosch remans because on occasion I've had to swap in four alternators to wind up with one that worked. And it failed a few weeks later.

Something doesn't make sense about what happened when you jumped power to the exciter terminal. Power is supplied to the warning light from the Hot in Run and Start circuit. When the alternator isn't working the exciter provides the ground for the bulb, thus causing it to light up. When the alternator is working the back EMF from the exciter stops the flow of current and turns the bulb off. When you jumped power to the exciter, that should have back biased the bulb and prevented it from lighting up.

[Tsx-kineticz]

ok in the bentley if u remove the exciter wire from the alternator and the idiot light is still on then that means you have a short from that wire to the cluster. .. that blue wire d+ goes straight to the cluster through c101 after the cluster it connects to the steering switch ( if im not mistaken)