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Alternator Hookup Question

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Old 07-24-2015, 08:17 PM
midniteblue midniteblue is offline
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Alternator Hookup Question

I have a 1978 Bronco with a 351M engine, and I'm in dire need of someone's help.

While replacing the old fan belts with new belts, I also decided to replace the old 60 amp alternator with a new one; however, in my haste to take things off, I neglected to make note of where the 3 wires should be hooked up on the back side of the new 60 amp alternator.

In following the color coded wires coming off the voltage regulator, where the regulator has the letters I-A-S-F, there's a red wire that comes from the "F" terminal, a light green wire that comes from the "S" terminal, and a white wire that comes from the "A" terminal.

The red and white wire then go thru a plastic sheath and come out at the other end of the sheath, where the alternator should be bolted in to its bracket. The light green wire does NOT go thru the sheath. Instead, the light green wire bends back toward the voltage regulator and disappears into a black rubber boot.

Where the red and white wires exit the sheath, there's also a thicker black colored wire with a round metal eyelet on the end of it that also exits the plastic sheath along with the red and white wires.

Based on an internet diagram I located, I think I know that the red colored wire, which as I mentioned above, comes off the voltage regulator's "F" terminal, is supposed to be hooked up to the alternator's "Field Terminal", and the white colored wire, which comes off the voltage regulator's "A" terminal, is supposed to be hooked up to the alternator's "Battery Terminal". But where is the thick black colored wire with the metal eyelet supposed to be hooked up??

If I'm correct about where the red and white wires should be hooked up on the back side of the alternator, the thick black colored wire should be hooked up to either the "Stator Terminal" on the back side of the alternator or the "Ground Terminal" on the back side of the alternator.

From what I've read, if I hook the wires up to the wrong terminals, I run the risk of blowing my electrical system, which undoubtedly would be disasterous for me.

I'm not sure where the thick black wire comes from even though I've tried to follow it. It introduces itself into the plastic sheath about half way between the voltage regulator and the other end of the sheath.

Any help from anyone who knows this stuff would be GREATLY appreciated so I can finish this "little" project.
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Old 08-02-2015, 10:53 PM
midniteblue midniteblue is offline
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So, after even more endless hours of internet research and talking to almost an even dozen guys who claimed to be mechanics, I finally ran across a guy who said he used to rebuild alternators for his own early to late 70's Broncos.

For anyone faced with a similar dilemma, this guy told me that the white colored wire attaches to the alternator's Stator terminal, the orange reddish colored wire attaches to the alternator's Field terminal, and the black colored wire attaches to the alternator's Battery terminal.

Every alternator wiring diagram I saw on the internet was different from the other, so I didn't know which one was right.

Now, all I need to do next is try and figure out why my engine started idling so rough. I've checked the vacuum lines and spark plug wire connections, but I don't see anything wrong in either place. Does anyone have a suggestion about what I should look at next?
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Old 08-09-2015, 11:41 PM
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Encho Encho is offline
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I'm glad you managed to find someone with the knowledge to help you, I actually had no idea.
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Old 08-31-2015, 09:05 AM
Bigpain2000 Bigpain2000 is offline
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I would check the timing by adjusting your distributor or carb. for the air fuel mixture.
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Old 08-31-2015, 03:58 PM
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Unless you moved the distributor around or it jumped time it wont be a timing problem.
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Old 08-31-2015, 04:32 PM
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Welcome to FTE

It has a carburetor, correct? I'd sure want to have that gone through regardless. When was it last rebuilt, you think? Maybe $20 for a rebuild kit with new gaskets and such.

Examine plugs for condition - fouled, glazed, deposits, etc. Bulletproof the ignition system with a good tune-up - wires and cap, and spring for new ground cables to block and firewall, battery to solenoid, etc. The 70s were a LONG time ago.

Can't always tell much just by looking at vacuum hoses and such. Connect a mechanic's type vacuum gauge to a source of constant manifold vacuum. This is the about the only effective way to hunt that kind of thing down. Very useful tool for engine diagnostics and tuning.
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