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type A: positive (+) 12V pulses from the switch to the factory relays
This security system can control Type A door locks directly, with no additional 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,
you must take care to ensure that it is not a Type C direct-wire system.
IMPORTANT! If you mistake a Type C direct-wired system for a Type A positive-pulse system, the
module will be damaged!
Here is a test: Cut the wire which pulses (+)12V on lock, and then operate the switch to unlock.
I If all doors unlock, the vehicle uses a Type A system.
I If you lose all door lock operation in both directions, you are operating the master switch in a Type C system.
I If one or more, but not all, motors stop operating, you have cut a wire leading directly to one or more motors.
Reconnect the wire and look for another wire.
Many domestically-made GM vehicles use Type A locks. However, many more GM vehicles are Type C than in pre-
vious years. The full-size pickups (1989-later), many of the S10 Blazers, the Corvette, '95 Cavalier/Sunfire 1993
and newer, Camaro/Firebird all use Type C door locks, and cannot be controlled without a 451M! Almost all domes-
tically-built Fords are Type C. Ford builds almost no Type A systems. Chrysler builds both Type A and Type C, so
test carefully.
IMPORTANT! Remember that the functions of these wires reverse between Type A and Type B!
© 2001 Directed Electronics, Inc. Vista, CA
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