Hi Simon - I'm going by the diagrams as the UK never had any of the same
systems as North America. The interlock system that prevented cranking under
various circumstances was indeed for the 74 and part 75 years. There is a
special section in the Leyland Workshop Manual showing the details of the
system, it did include a buzzer, but in exactly what circumstances it sounded
the buzzer and opened the interlock I don't know. I would expect the seat
belt warning to include the buzzer, but whether it sounded on turning on the
ignition, or just turning to crank, I don't know. There were earlier (part 72
and 73) and later (part 75 on) systems that didn't include the interlock, but
both did include a buzzer. The earlier system purely uses switches and it's
possible to work out that the seat belt warning did include a buzzer, as did
the 'key in' warning. The later system uses a simplified (from the 74/75) box
of electronics containing the buzzer so again it isn't possible to determine
from just the diagram under what circumstances the buzzer sounded.
----- Original Message -----
When I had a US-spec '74 B, the system would sometimes prevent the car
from starting. I am fairly sure that the system acted as an interlock
with the starter circuit....
I think the buzzers came later, when the interlock was removed.
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