In short, alternator failed on me Friday night, but did not get stranded...made it home 40 miles away no problem.

While removing the alternator, I noticed a wire hanging freely with the rest of the wiring harness. It had electrical tape around the lead. First impression was, "That's my problem right there"...not.

Yanked out the alternator and had it bench tested...1-2 volt output...need new alternator. Found exact replacement at great price. Recharged battery, all is well now.

Question is, that lone loose wire. The harness has a thick hot wire to the alt and a thin ground to the alt. 2 other wires go to the oil sending unit. The last wire I cannot figure out. The connecter on it has a small round copper plug type. Since my alt. is a Paris Rhomes (sp?) and is a 2 lead, is it possible that the loose wire is for the 3 lead type alt. like a Bosch or something? If not, what is it for, I looked all around the vicinity and there is nothing for it to connect to.

Keith Widom



Any chance it is kind of aqua blue?

If it is it is the oil level sender lead. Those things are always hanging down there. It is supposed to be tie wrapped to the alternator bracket then go over to the front right of the motor on top of the oil pan.

Jay Kempf


Keith, this has probably already been answered, but, here anyway is more info.

The thin wire is not a ground. It is the exciter lead that comes from the ignition switch circuit. You have to feed electricity TO an alternator in order to get electricity FROM an alternator. Obviously you happened to hook the "ground" wire to the right place or you would have been blowing fuses.
(It looks like a ground, but it actually insulated from the frame by fiber washers which you didn't notice. I was just there; I just replaced my Paris-Rhone a week ago -- $135 from NAPA) (sorry big 3).

For the mystery wire, look on top of the front edge of the oil pan where it sticks out kind like an aggressive chin. On top of there, on the port side is the oil level sensor (has a float down in the oil). The connection to this sensor is kind of a little round thing like an old lawn mower engine spark plug. Just touch it to ground with the engine running and see if your
assistant in the driver's seat notices an oil level light going on.



The large terminal B+ on the alternator is a junction point. Power runs into the point from the battery and to the accessory lead of the car. When the engine is running the alternator is putting power out to both the car and to charge the battery.

Depending on the alternator the slide connector could be a duplicate D+ or a ground. Often the D+ will have a bolt on slide connector. Anyway the small wire should go to the D+ terminal.

Dan the Pod Guy
Portia's Parts

-----Original Message-----
Subject: Alternator wiring
From: =?ISO-8859-1?Q?Ron=20Disney?= <>
Date: Sat, 01 Apr 2006 18:14:57 -0800
X-Message-Number: 41

I have a 1980 US Auto. I am reinstalling the alternator and don't know = where what cable goes where.
My alternator has a large nut connector labeled B+, a smaller nut = connector labeled D+ and a slide on connector with no label.
I have two large cables with the same size washer connector and a small = wire with a slide on connector.
Do both large cables go to B+?
Or the hot one to B+ and the other to D+?
The slide on one is obvious


It's alive!


Here's a simplified schematic for S4, GT and GTS. Other models are very similar.


1992 928GTS midnight blue