Showing the additional contact for the purple/pink wire: When the key is inserted a pin pushes the spring (arrowed) against the body of the lock to connect an earth to the wire, which if the driver's door is opened sounds the warning buzzer. Testing has shown that this only happens when the switch is in the 'OFF' position, however one would expect that it should also be operated in the accessories position. On the face of it, it doesn't need to be operated if the engine is running (should be obvious ...), but that still leaves the situation of no warning buzzer if the engine has stalled and the ignition is still switched on. (Arthur Johnson, restoring a 1972 ex-California GT in Australia)

One of two North American 1973 cars where the warning buzzer sounds if the steering is not yet locked, even though the key has been removed. Different to the one above, this one has the connection inline with the locking pin, instead of at the side of the lock. The wiring is otherwise the same: (Arthur Taylor)