Overcharging
My 75 Scamp just started overcharging last week. New vr,control module and battery. The alternator is fairly new. Completely bone stock and untouched under the hood. I will try some of these tricks.
1. No tricks involved. Set up situation and check the voltages at the connecting locations and current flow to or from the battery.
2. '75 has some wiring differences from earlier models. The changes are not as radical as '76, but the first thing will be to get a '75 FSM and sketch out the charging circuit. You want to be looking at the correct colors and connections!!!
You may notice there were some optional ways to wire the cricuit depending on how the car was equiped.
The next thing to do is a visual check of the lines.
Your looking to see
....if it matches the FSM.
...if there is corrosion, oxidation, broken strands at any of the terminal connections.
...signs of overheating
...chafed worn, cracked insulation on the wire themselves.
Start at the battery positive because that's easy to see. Follow it to the bulkhead connector.
Then go to the alternator's output stud (aka alternator battery terminal). Follow it to the bulkhead connector.
This where you will need the factroy wiring info - the alternator output wire gets a wrapped into a harness with other wires, you can't visually follow it easily if at all.
Then check the regulator and field circuit. It's power comes from the 'ignition 1' or run circuit feed.
Once you know where everything is, at least engine bay side, you can do checks with a voltemeter.
Don't forget to observe the ammeter. Together they will reveal the story.