Strange Headlight problem
Need to look at how the car is optioned. Could be an atypical item such as the headlight warning light/chime that relates to the key switch.
I say this because the basic headlight system does not involve the key switch. Headlights and the parking lights and the instrument lights all can be powered with the key off. Since the problem occurs with key on, and goes away with key off, it must be related to the key switch or a cross wire short to circuits turned on by the key switch.
Main circuits for a '72 (w/ a standard alternator, and points ignition)
Need to look at how the car is optioned. Could be an atypical item such as the headlight warning light/chime that relates to the key switch.
I say this because the basic headlight system does not involve the key switch. Headlights and the parking lights and the instrument lights all can be powered with the key off. Since the problem occurs with key on, and goes away with key off, it must be related to the key switch or a cross wire short to circuits turned on by the key switch.
Main circuits for a '72 (w/ a standard alternator, and points ignition)