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Old 08-07-2020, 11:18 AM   #1
tbrown5079
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Resistor on alternator exciter feed

How important and how many guys are using a resistor on the exciter feed wire on a stand alone LS application? 470 ohm? I converted the original alternator regulator with a regulator for a 2004 Silverado and it worked for 5 years and several thousand miles but went bad. Replacing it with a new one but wondering if I should add the resistor for longer life. Your thoughts.
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Old 08-07-2020, 07:24 PM   #2
ls1nova71
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Re: Resistor on alternator exciter feed

If the PCM is controlling the alternator than you dont need the resistor. Resistors are for those not using the computer to control it.
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Old 08-07-2020, 10:31 PM   #3
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Re: Resistor on alternator exciter feed

OK, thanks. I only have the exciter wire in and the power wire out, so I added a 470 ohm resistor. Seems to work ok, trying to make this one last longer. Thanks.
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Old 08-08-2020, 09:34 AM   #4
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Re: Resistor on alternator exciter feed

install a simple 12 volt lamp and it will last forever. that's how GM did it for decades. the lamp will survive current surges that will burn up a resistor and a lamp is a tell take visual indicator of functionality. the whole concept of a resistor is not ideal especially when it burns up and you are broke down in the middle of no where.
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Old 08-08-2020, 12:40 PM   #5
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Re: Resistor on alternator exciter feed

OK, thanks. I will try that.
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Old 08-09-2020, 01:26 PM   #6
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Re: Resistor on alternator exciter feed

85 ohm resister is the needed number
I picked up echlin ec 82 pigtail adapter with resistor installed
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Old 08-09-2020, 03:29 PM   #7
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Re: Resistor on alternator exciter feed

Good information. Sounds like that is definitely what I need. Thanks
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Old 08-23-2020, 09:14 PM   #8
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Re: Resistor on alternator exciter feed

So gmc684X4, how did you wire in the Echlin ec82? I got mine yesterday, but only needing one wire to the alternator I'm not sure how to wire it in. Do one of the plugs actually fit in the alternator? Thanks for your help. tbrown
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Old 08-24-2020, 11:15 AM   #9
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Re: Resistor on alternator exciter feed

I removed the second wire i have been thinking about asking american auto wire about that second wire
I looked at original prints for 88 up trucks they dont use the second wire just like the donar altenators i pulled out

I changing the alt for my 72 to a cs144 that i pulled from a 99 express van delayed dropping in an engine into my truck getting head work done for my new engine instead of using a short term motor that will need a different clutch
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Old 08-24-2020, 01:34 PM   #10
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Re: Resistor on alternator exciter feed

https://alternatorparts.com/ad244-se...regulator.html
Here is a possible solution. One wire exciting regulator if your going to change from the factory 2 wire regulator that is computer controlled.
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Old 08-25-2020, 06:54 PM   #11
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Re: Resistor on alternator exciter feed

Guess I still don't understand why you feel the need to put in a resistor if the alternator is PCM controlled? If you are not using the PCM, then yes, you would need it, but since you said you have driven it several thousand miles without one, I am assuming its PCM controlled or it wouldn't have gone that long.
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Old 08-27-2020, 12:05 PM   #12
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Re: Resistor on alternator exciter feed

Thanks for the replies. To clear things up, it is not pcm controlled. Only a exciter wire and output. I used the original alternator from the 2007 gmc truck, and revamped it with the regulator from the site that was recommended here. It failed a couple of weeks ago so I went with the 2004 Silverado alternator we were trying to mimic for longevity. Just trying to do my best and upgrade it as close as possible. I installed the light socket that was recommended but wanted something more technical. That is why I wanted to wire in the Echlin ec82 harness. Hope this makes some sense. Thanks. tbrown
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Old 08-29-2020, 10:04 PM   #13
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Re: Resistor on alternator exciter feed

I don't understand the 82 ohm resister value. The original had a light bulb and also a 'resistor wire' that was in parallel. The reason for the wire was so if the bulb burned out you would still be charging. If I remember what I read, the bulb would be about 8 ohms and the wire would also be 8 ohms. Since they were in parallel the total would be around 4 ohms.
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Old 08-30-2020, 12:18 PM   #14
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Re: Resistor on alternator exciter feed

To me it appears you guys are pulling info from multiple sources which conflict.

I have never seen any parallel wires/resistors in GM wiring diagrams. I have never seen any wire (with resistance) other than the ignition power wire that feeds the points on older gm vehicles. Its actually NICROM wire (nickle chromium) which drops voltage more han pure copper wire. The ignition switch would bypass the resistive wire during cranking, to give the condenser and coil a full 12v then once the ignition switch was in the run position, it would power the coil at a lower voltage.

Why not wire it same as GM did in the older vehicles or like the gen 3 diagrams and let the alternator monitor voltage and send that signal to the alternator/regulator and let it do its work?

Please provide your source docs/links for this parallel wiring you are discussing.
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Old 08-30-2020, 09:25 PM   #15
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Re: Resistor on alternator exciter feed

aknovaman Check http://67-72chevytrucks.com/vboard/s...d.php?t=746675.
You can see diagram as well as explanation.
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Old 12-04-2020, 08:06 PM   #16
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Re: Resistor on alternator exciter feed

Quote:
Originally Posted by tbrown5079 View Post
Thanks for the replies. To clear things up, it is not pcm controlled. Only a exciter wire and output. I used the original alternator from the 2007 gmc truck, and revamped it with the regulator from the site that was recommended here. It failed a couple of weeks ago so I went with the 2004 Silverado alternator we were trying to mimic for longevity. Just trying to do my best and upgrade it as close as possible. I installed the light socket that was recommended but wanted something more technical. That is why I wanted to wire in the Echlin ec82 harness. Hope this makes some sense. Thanks. tbrown
GM used light bulb for over 50 years
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