Burnt Wire

^^Basically^^

You need to "shed the load" so you can isolate the problem. Since the problem (right) only shows in the "start" position, you will have to eliminate other loads so the lamp goes dim, and "is only lit" by the short

So disconnect the wire on the starter relay that connects to the "square" screw on the starter solenoid. This is the solenoid connection. It actually does NOT go through the ammeter but it will light your test lamp

Try again if the lamp is still bright

Disconnect either of the "push on" terminals on the starter relay

If the lamp is still bright

Disconnect the VR connector, it should not make much difference.

Next disconnect the ballast resistor

If none of these make much difference in the lamp brightness, start at the "dark blue" at the ballast resistor and chase it back to the bulkhead connector in the engine bay. Look for frayed/ broken insulation, burned areas, or something "non original" spliced into the blue wire

Examine the coil wire and look for damage/ short. Go back to the ballast and examine the remaining terminal should have a brown and another wire. Examing that for damage. Disconnect the coil+ wire. Try again twist the key look for any change in lamp brightness

Now go down to the alternator and examine the light blue wire, look for burned/ bad insulation, chase that wire back to the bulkhead, looking for damaged harness, etc.

If none of this gets you anywhere things are going to get complicated