70 Dart Stopped Charging

The ammeter laying over MAY be because the battery is down quite a bit

Measure the battery voltage right at the battery terminals, watch voltage and the ammeter and raise RPM while doing so.

If the voltage stays below 15V but the ammeter lays over, then the battery is simply low, and it's charging

You description therefore is contradictory. You say the "large terminal" (where on the alternator?) is 14.5--------(when---at all times, with engine revved, ??)

Do the lights seem OVERLY bright? Again, if the battery is low, the lights would be DIMMER than normal with engine off or idling slow, and might be simply "coming up to normal" with system voltage at 14.xx