Re: Alternator Not Charging 1971 Roadrunner
[Re: markshemiworld]
#2770457
05/02/20 02:31 PM
05/02/20 02:31 PM
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Joined: Dec 2004
Posts: 10,555 Rittman Ohio
fourgearsavoy
I Live Here
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I Live Here
Joined: Dec 2004
Posts: 10,555
Rittman Ohio
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First you need a multi meter (even an el-cheapo from HF ) put it on the DC volt scale and check voltage at the large black wire on the alternator. Did your older alternator work at all? Did it keep the battery charged? Gus
64 Plymouth Savoy 493 Indy EZ's by Nick at Compu-Flow 5-Speed Richmond faceplate Liberty box Dana 60
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Re: Alternator Not Charging 1971 Roadrunner
[Re: markshemiworld]
#2770475
05/02/20 03:44 PM
05/02/20 03:44 PM
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Joined: Jan 2003
Posts: 25,858 Rio Linda, CA
John_Kunkel
Too Many Posts
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Too Many Posts
Joined: Jan 2003
Posts: 25,858
Rio Linda, CA
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If you have the original green and blue wires to the fields, check that the blue wire is providing 12V when the ign. sw. is ON. If good, remove the green wire and temporarily ground the green terminal...this should sent the alternator into max charge.
The INTERNET, the MISinformation superhighway
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Re: Alternator Not Charging 1971 Roadrunner
[Re: markshemiworld]
#2770483
05/02/20 04:06 PM
05/02/20 04:06 PM
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Joined: May 2019
Posts: 6,281 nowhere
Sniper
master
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master
Joined: May 2019
Posts: 6,281
nowhere
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You alternator has three wires hooked up to it.
the fat black one you mentioned, that is the output, it goes to eh battery via the ammeter.
A blue wire, this one comes from the ignition switch and provides a switched 12V to the alternator so it can operate.
A green wore that comes from teh regulator, this is what controls the alternator output.
The black wire should have 12V on it all the time The blue wire should have power on it when the key is in run.
If neither of those is true you have a wiring issue.
The green wire will have a variable voltage on it is it's controlling and the key is on. Grounded turns the alternator on to max, 12v turns it all the way off, somewhere in between it's putting out something more than nothing, but less than max (sorry no output chart that I know of).
You can temporarily remove the green wire from the alternator connection and replace it with a jumper wire, if you ground that jumper with the engine running and the other wires all hooked up it should make the alternator charge. If it doesn't the alternator is bad. If it does you have a wiring issue. Just connect the jumper long enough to verify charging is happening. You meter can tell you that or you can take a quick look at the ammeter.
Tell us what you find.
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