jcmoretti

I put a new 12Si alternator in my car a month or two ago. I wired brown from the regulator harness to '1' and red to '2', BAT to the horn relay, and have had no problems. Charging is/was fine.


Yesterday I moved the car twice in the driveway to clean it up. Then I went for a ride and at my destination, it wouldn't shut off with the key. I ended up pulling a wire off the alternator to get the car to stop. I did this three more times throughout the day.


When I got home I measured the voltage.. 16.5... I am used to 14.2 or so. Also I checked that with the car off, that the brown wire responds to the cycling of the key, as does the ignition feed (I have and HEI). However, when the car is running, both of these stay hot even with the key in the off position. Any thoughts on what else I can test to rule out a bad alternator? I think it is under warranty but I want to check everything I can before I pull it. Thanks.

don71

A couple of things come to mind....

Does your GEN lamp light up when key in on?

The brown wire is the feed for the GEN lamp, and (the lamp) can act like a resistor for back feed. My theory is....if the lamp is out you no longer have that action.

I'm not the expert on this issue, that is simply my understanding of it.

I have read where people install a diode in this circuit to prevent this very thing from happening, this is usually associated with after market ignition systems though.

Also, 16.5 volts that would be a concern for me. That is the upper limit of the voltage regulator. Like you said, 14.2 would be quite normal.

jcmoretti

My GEN lamp does function. It illuminates when I turn the key to the on position, prior to starting. Then goes out while the car is running. When I then turn the key in an attempt to shut off the car, it illuminates again until I kill the alternator by pulling a wire.

don71

Yes I meant GEN light. Hopefully someone can help you another approach to your issure.

jcmoretti

Just to close this out... I ended up swapping the alternator and the problem went away. Previously I mentioned getting over 16 volts from the defective unit but I only saw that after a 45 minute drive on the day the car started acting up. Subsequent tests were always in the 14v range but I still couldn't get the car to shut off with the key.


Fortunately I bought the alternator at Autozone (part number DL7292-9) and I was able to get it replaced under warranty. Note that the counter person tested the defective unit and it passed their test criteria. He still agreed to swap it out for me and that did indeed appear to be the culprit.