Factory ammeter
It should not result in the battery overcharging. 14.5 Volts at the battery is normal and the battery should charge normal unless it is run down, low on acid or otherwise damaged.
If it is very low on charge, it will draw a lot more current than when slightly low. (See the photo sequence in this post for example of this.)
To narrow down the problem, check
The Ammeter reading. The ammeter will indicate how much current is flowing to the battery for recharging.
Since the battery charge rate may change (should go down as the battery recharges after start), recheck the ammeter after making voltage measurements.
Recheck the voltages at the alternator output and the battery.
This time also check the voltage as close to the voltage regulator as you can probe. (read post 67 for more details)
Additionally, check for voltage drops in the ground path between the body and the alternator housing.
Check for voltage drops in the ground path from the battery. Note the ammeter reading even if zero. This very important.
With an analog meter the black probe will need to be on the ground of the power source.
If the voltage drops in the ground bath that current is flowing is minimal, then procede to look for voltage drops in the output lines and connections.
Post back here with what you're finding and people can help.
Note: If the ammeter is pegged or close to pegged, shut the engine off! Stop testing. Get the battery fully charged on a charger and if possible tested.
A pegged ammeter is a shutdown situation.
Note 2: Visually check the power circuit wiring. It probably looks something like the diagram, but especially for '75 this should be verified. If the car has rear window defroster grid it will have a slightly diferent wiring path. Some have mentioned seeing remote shunt ammeter wiring on '75s. If you see multiple fusible links, that would be an indication of this or a heavy duty wiring arrangement.
Ok. First - Do you mean the ammeter is showing charge all the time?
This means there is resistance to flow between the alternator and the battery.
It should not result in the battery overcharging. 14.5 Volts at the battery is normal and the battery should charge normal unless it is run down, low on acid or otherwise damaged.
If it is very low on charge, it will draw a lot more current than when slightly low. (See the photo sequence in this post for example of this.)
To narrow down the problem, check
The Ammeter reading. The ammeter will indicate how much current is flowing to the battery for recharging.
Since the battery charge rate may change (should go down as the battery recharges after start), recheck the ammeter after making voltage measurements.
Recheck the voltages at the alternator output and the battery.
This time also check the voltage as close to the voltage regulator as you can probe. (read post 67 for more details)
Additionally, check for voltage drops in the ground path between the body and the alternator housing.
Check for voltage drops in the ground path from the battery. Note the ammeter reading even if zero. This very important.
With an analog meter the black probe will need to be on the ground of the power source.
If the voltage drops in the ground bath that current is flowing is minimal, then procede to look for voltage drops in the output lines and connections.
Post back here with what you're finding and people can help.
Note: If the ammeter is pegged or close to pegged, shut the engine off! Stop testing. Get the battery fully charged on a charger and if possible tested.
A pegged ammeter is a shutdown situation.
Note 2: Visually check the power circuit wiring. It probably looks something like the diagram, but especially for '75 this should be verified. If the car has rear window defroster grid it will have a slightly diferent wiring path. Some have mentioned seeing remote shunt ammeter wiring on '75s. If you see multiple fusible links, that would be an indication of this or a heavy duty wiring arrangement.