Alt. signal wire

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Raider L

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William
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1974
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C10
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355
@SirRobyn0,
Yeah, I do the same. I looked at that page in the maint. book and thought, "Now, when the heck would I need something like that?" Heck, I'll just hook an ohm meter to it. There's only like a million videos on checking stuff electrically.
Yeah, I'm the same about starting. That MSD 6A box I've got on there fires each plug six (6) times at start. If it takes more than about a half a turn of the crank with that much fire, you got some other problem. You're out of gas!!
 

olnick

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Milford NH
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Nick
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1978
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c15
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1982 350 4 bolt mains
From page #1 of the original problem: (Alt sense wire cooked) My first thought was that the voltage regulator was shot! As the "sense" wire does just that, sense the voltage of the "at use" voltage of the main electrical system in the truck. This wire only tells the regulator what the operating system voltage is under the current load conditions eg. with a heavy load (high beams and heater on high). the voltage drop from the alternator output to the main system feed is what this wire senses (detects) this in turn tells the regulator to crank up the output to compensate for the above mentioned voltage drop from the alternator feed wire. This is referred to as an "active"voltage regulator as it constantly monitors the current in use voltage in the main wiring harness. When the voltage regulator goes bad (sense terminal shorts to ground internally) the sense wire is still connected to the main harness unfused 12 volt feed and melts. A #24 .015 gauge wire is more than enough to handle the voltage ONLY signal needed to remotely adjust the regulator output to the current needs of the truck.
 

Raider L

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William
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C10
Engine Size
355
@olnick,
Thank you. That makes perfect sense and is what probably happen. What puzzled me though was that I had just rebuilt that alternator including a new rotor, voltage regulator, diode trio, everything...except the stator. It was the factory original from 1974. As long as it tested okay I reused it everytime I rebuilt the unit, like for decades! Now, I mostly just put in a new voltage regulator every time something went bad, usually the voltage regulator. It was either going to high, or wouldn't hold it's prescribed voltage. I noticed over the years that as more parts venders went to China that stuff got worse and worse. And that's probably what happened this time. I had been trying to find a U.S. made from a reputable dealer or maker 14.6 volt regulator but could only find a Chinese made 14.2v or 14.8v. Well, with everything on, i.e., lights on high, wipers, fan on high, etc., it didn't seem the 14.2 could put out what I like seeing, no less than 14 volts, and if the regulator went bad for some reason the 14.8 would be into 15 volts and I didn't like that either. Or it would be waving around, I'd seen that before to.
So I think I had one of those, new in the rebuilt alt., didn't like it and had another new one, a 14.2v, and it had been in there for about six months when the signal wire caught fire. Then I went and bought a brand new alternator for the first time in probably forty years and when my rebuilt one went bad I put that new one in the truck but even then changed out the voltage regulator, like I said and that's what's in the truck now. But you see how I isolated all the alternator wiring so in case anything happend again, God forbid, it won't burn the heck out of all my other wiring in the process. What took me so long to do all I did was I had to repair all the burnt wiring, then I went back through all the wiring from the alternator all the way through the inside of the under dash wiring to everywhere the alt. wiring went, and why. I then repaired some splices I didn't like from the factory, you woukldn't believe the crappy wiring I found I hadn't noticed before. And resoldered all the factory splices and put heat shrink on all of it.
 

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