1972 914 Tail Light Electric Circuit Question

[Hannum]

Does anyone have suggestions regarding an electrical glitch in my tail light (NOT brake light) circuit? When the key is turned on, with either the motor running or just to power up the car, both tail lights light up. These are the tail light filaments of the dual filament bulbs in the center portion of each tail light assembly. The tail lights operate both when the headlight switch is engaged, as well as remaining alight when the switch is dis-engaged...so long as the key is turn to either "on" setting (running or just "power-on"). The brake lights function normally as they should and only operate when the brakes are applied. The rest of the electric functions in the car operate normally. Any trouble shooting suggestions?