electrical problem...?

[Nick_S]

Having identical issues...bumping this thread

My issues started immediately after jumping a friends car.

[nando]

Operation of the alternator in an all but very late production E30's requires that the alternator/battery warning light in the cluster be good. That light should come on when the ignition is on and go out when the engine fires. If the bulb is burned out, there is a problem in the cluster, or in the exciter circuit the alternator won't work properly.

Actually, there is a resistor from at least 1988 build dates as a failsafe if the bulb burns out. I havent looked at earlier builds to see when they added it but it wasn't just late cars.

[jlevie]

The light comes on with ignition and off when engine fires. That cluster bulb is not the problem.

Okay, so the exciter seems to be good. The next things I'd check would be grounding of the alternator and the power out connections.

[LuCifer]

Maybe something is killing the alternators.

Possibly, but what? Lol

[b*saint]

Maybe something is killing the alternators.

[LuCifer]

Operation of the alternator in an all but very late production E30's requires that the alternator/battery warning light in the cluster be good. That light should come on when the ignition is on and go out when the engine fires. If the bulb is burned out, there is a problem in the cluster, or in the exciter circuit the alternator won't work properly.

The light comes on with ignition and off when engine fires. That cluster bulb is not the problem.

[jeffnhiscars]

Operation of the alternator in an all but very late production E30's requires that the alternator/battery warning light in the cluster be good. That light should come on when the ignition is on and go out when the engine fires. If the bulb is burned out, there is a problem in the cluster, or in the exciter circuit the alternator won't work properly.

Hard to believe they put something as critical as the alternator at the mercy of a $2 bulb.

[jlevie]

Operation of the alternator in an all but very late production E30's requires that the alternator/battery warning light in the cluster be good. That light should come on when the ignition is on and go out when the engine fires. If the bulb is burned out, there is a problem in the cluster, or in the exciter circuit the alternator won't work properly.

[LuCifer]

The alternators have been bosch rebuilds. Ive read that the 140 amp alt. in a 7 series has a relay for it. The e30 does not, could that be the problem?

[jlevie]

Monitor system voltage while the car is being driven. That will tell if the alternator is working and how well.

If you are using generic reman alternators, you may go through several before you get a good one. As a result of an experience with multiples being bad I no longer use anything but a factory reman. They are more pricey, but I've never had a bad one "out of the box" or one that fails shortly after installation.

[LuCifer]

Swapped out the new alternator for another one. As soon as it was installed Volts were up at 14.1. Car ran great for the rest of the day yesterday, drove home, out at night, drove back home, to work this morning and everything was fine.

As i'm leaving work today I notice it seemed weaker on starting up. As i'm driving home the same things start to happen all over again. Any ideas?

[LuCifer]

Bump

[LuCifer]

To isolate the problem a little further, remove the exciter lead from the alternator and see what voltage it shows when the ignition is on. It should be at battery voltage. If it is and is at 11.2 when connected to the alternator, either the alternator isn't grounded or the alternator is bad.

Just did what you said. When disconnecting the exciter stud, with ignition on, there is no voltage at all. Output stud still reads 11.2. What does this mean now?

[jlevie]

To isolate the problem a little further, remove the exciter lead from the alternator and see what voltage it shows when the ignition is on. It should be at battery voltage. If it is and is at 11.2 when connected to the alternator, either the alternator isn't grounded or the alternator is bad.

[LuCifer]

With the engine idling, what is the voltage on the exciter stud and what is the voltage on the output stud. And is there any voltage difference between the alternator body and a chassis ground point?

The voltage on both studs reads 11.2. The alternator body is grounded. Didnt check the chassis ground point.