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© 2006 directed electronics.
type A: positive-triggered, relay-driven system
The system can control Type A door locks directly, with no addi-
tional parts. The switch will have three wires on it, and one will
test (+)12V constantly. The others will alternately pulse (+)12V
when the switch is pressed to the lock or unlock position.
If you cannot get to the switch, and you find a set of wires that
pulse (+)12V alternately on lock and unlock, make sure that it is
not a Type C direct-wire system.
Here is a test: Cut the wire that pulses (+)12V on lock, and then
operate the switch to unlock.
■ If all doors unlock, the vehicle uses a Type A system.
■ If you lose all door lock operation in both directions, you are
operating the master switch in a Type C system.
■ If you lose all door lock operation of one or more, but not all
motors, and other doors still work, you have cut a wire leading
directly to one or more motors You must reconnect the wire and
search again for the actual wires leading to the switch.
Many domestically-made GM vehicles use Type A locks.
However, many more GM vehicles are Type C than in previous
years. The full-size pickups (1989-up), many of the Blazers, the
Corvette, ‘95 Cavalier/Sunfire 1993 and the newer,
Camaro/Firebird all use Type C door locks, and cannot be
controlled without a 451M. Almost all domestically-built Fords
are Type C. Ford builds no type A systems. Chrysler builds both
Type A and Type C, so proceed with caution.
important: Remember that these wires’ functions reverse
between Type A and Type B.
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