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Old 05-12-2009, 05:50 PM
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Mopar Ron Mopar Ron is offline
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SORRY another 3 wire GM alt question

I have a 40 dodge PU with a 318 dodge engine in it and I put a 3 wire gm alt on it and had the infamous run on problem and after going back and forth with the #2 and #1 wire to the batt post on the alt, we wired it right with the #2 going to the batt post and the # 1 going inside the truck to a ing feed with the key on but then as you know it would not turn off with the key.
now I didn't want to run a light and after we discussed this problem with some other streetrod guys they said I need to hook the #1 feed wire to the ACC side instead of the run side and that made total sense, so I went home and did that and sure enough it works fine, I have had it like this for about 8 month now.

now I was posting on another site about how it is now wired and this is a reply that i got:

You don't want to do that. I'll guarantee you --unless these units have been changed electrically by GM--that if you do that long enough you'll blow up a diode trio. I don't remember all the "ins and outs" but there are situations where the diode trio can "try" to become the source (charge, or supply source) and they won't handle much amperage. The original cars had a resistor / lamp combo, so you either need that or the diode.


My answer:
I don't know what you mean by "long enough" but last year I had a charging problem and the run on issue and with my 40 dodge PU with the gm alt and I was tring different things with the # 1 wire and the #2 wire and after talking with a bunch of streetrod guys we figured out that the reason it was running when the key was turned off was because it was being feed from the #1 wire to the Ing run side and I needed to either put a lite in line like GM does or just get the power to the #1 wire from the ACC side. so that is what I did and for 8 month now it works just fine Ron..



I think you misunderstood. It WILL work "just fine" for ahwile, but you need the diode/ or resistor/ light in there to protect the diode trio in the regulator. By "long enough" I mean "some period of time." Might be a week. Might be a year. I don't remember the mechanics of this failure, but there are/ is a certain condition which can cause the trio to become a source of power and the small trio diodes won't handle the load. This is a well documented failure, and is why the no1 is hooked up this way.


so does that sound right,will this way fail??? thanks in advance, Ron...
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