77 C3 Alternator
Thread Starter
7th Gear
Joined: Aug 2024
Posts: 7
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From: Eastern Shore, VA
77 C3 Alternator
Hey all, quick question about the alternator on a 77. I'm getting 11.3V at the alternator, so I'm assuming that's bad. But I am reading there is a internal voltage regulator, does anyone know a way to tell if it's the alternator or regulator that has gone bad? Thanks for the help.
Melting Slicks
Joined: Sep 2016
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From: Wauconda IL
Race Director
Joined: Nov 2006
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From: Sunshine Coast, Queensland, Australia
2025 C3 of the Year Finalist - Modified
2024 C3 of the Year Finalist- Modified
2022 C3 of the Year Finalist - Modified
Cruise-In VIII Veteran
You can purchase a rebuild kit fairly inexpensively. Try to find a nice name brand kit, not the cheapest kit. Regulator and diodes are part of the kit. Throw a kit threw it. See what happens.
On my 77 the windings started breaking down about 15 years ago already. This didn't cause a zero charge like you have however. But it did reduce the effectiveness of the alternator.
With electric fans this became a real issue.
At that time I upgraded to a 100 amp aftermarket replacement. And, frankly, there not that expensive.
Nowadays I run a Tuff Stuff 140amp unit. I have a fair bit of extra electrical load now.
On my 77 the windings started breaking down about 15 years ago already. This didn't cause a zero charge like you have however. But it did reduce the effectiveness of the alternator.
With electric fans this became a real issue.
At that time I upgraded to a 100 amp aftermarket replacement. And, frankly, there not that expensive.
Nowadays I run a Tuff Stuff 140amp unit. I have a fair bit of extra electrical load now.
Last edited by 4-vettes; Jul 23, 2025 at 02:42 AM.
Intermediate
Joined: Apr 2013
Posts: 26
Likes: 0
From: Spring TX
Run a 6AWG wire from your alternator to your starter and a 6AWG wire from the alternator and ground to the frame. This will help disperse any extra current and help keep from burning up any of those 40 to 50 year old small wires. Just a small trick I learned from a mechanic if you upgrade the amperage on you alternator.
Melting Slicks
Joined: May 2021
Posts: 2,274
Likes: 1,321
From: Fleming Island, FL
Hey all, quick question about the alternator on a 77. I'm getting 11.3V at the alternator, so I'm assuming that's bad. But I am reading there is a internal voltage regulator, does anyone know a way to tell if it's the alternator or regulator that has gone bad? Thanks for the help.
This will by-pass the voltage regulator and provide a full field.
Tech Contributor
Joined: Aug 1999
Posts: 14,380
Likes: 6,391
From: At my Bar drinking and wrenching in Lafayette Colorado
Just e-mail me for my alternator tech paper - it shows you how to disassemble and test every component in the alternator and set it up to work right. The components that usually fail are easily identified and replaceable.
Lars
V8FastCars@msn.com
Lars
V8FastCars@msn.com
