
TESTING: Door Locks
There are three basic types:
“Type A” Door Lock Test (Most GMs and some Chryslers)
Probe both of your door lock wires going to the door lock switch usally located in the driver’s
kick panel. Attach the clip end of your test light to a good chassis ground. Using the vehicle’s
door lock controls, activate the lock then the unlock, testing both wires one at a time. If one
of these wires tests (+) positive when lock is pressed and the other tests (+) positive when they
are unlocked, your vehicle has a “Type A” door locking system. Make sure to mark which wire is
lock and unlock. Proceed to Connecting Door Locks, Connecting Door Locks. NOTE: “Type A” and “Type
C” locks will test the same, until you test for ground. Make sure you run both tests before making
your connections.
“Type B” Door Lock Test (Most Imports, some newer Fords)
Probe both of your door lock wires going to the door lock switch usally located in the driver’s
kick panel. Attach the clip end of your test light to +12V. Using the vehicle’s door lock controls,
activate the lock then the unlock testing both wires one at a time. If the test light illuminates
when you probe the lock and the unlock wires your vehicle has a “Type B” door locking system. Make
sure to mark which wire is lock and unlock. Proceed to Connecting Door Locks.
“Type C” Door Lock Test (Most Fords, some Chryslers, GM Trucks)
(Optional part #778 required)
Using your test light probe both the lock and the unlock wires usually located in the driver’s
kick panel. Attach the clip end of your test light to ground probing both wires one at a time
while locking and unlocking the doors with the driver’s side switch (usually the master switch).
The test light should illuminate in both switch positions. Now attach the clip end of your test
light to +12V constant, probe both wires one at a time again. The light should then illuminate
again only in reverse order. This tells you that you have a “Type C” reversing polarity system.
Make sure to mark which wire is lock and unlock. Proceed to Connecting Door Locks.
CONNECTING “TYPE B LOCKS”
• If your vehicle has a “Type B” door locking system,
connect the GREEN WITH BLACK STRIPE wire from the
18-pin harness to the door lock wire. Connect the
BROWN WITH BLACK STRIPE wire to the unlock wire.
See diagram below.
“Type B” - Negative type door locks used on most
imported vehicles and some newer Fords. BROWN/BLACK
LOCK
UNLOCK
GREEN/BLACK
CONNECTING “TYPE C LOCKS”
•If your vehicle has a “Type C”door locking
system, you will need to purchase optional part
#778. Once you have purchased the relays, follow
the diagram on page 18 for “Type C”door locks.
TYPE C - (Optional Part #778 required)
Reverse polarity door locks. Used on most GM
trucks, Ford and Chrysler vehicles.
87a
BLACK
RED
BLUE
BLUE
YELLOW
WHITE
BLACK
RED
NOTE: When testing the door pin wire, make sure
the dome light is on. Some vehicles, if the door
is left open for a period of time, the dome
light will go out, resulting in a false reading.
DOME LIGHT (Optional Part #775 required)
To determine if your dome light is turned on
with (+) positive or (-) negative trigger,
probe for a wire in the driver’s side kick
panel that switches polarity when the door
is closed then opened. You can also find this
wire going to the under dash courtesy lights.
•If this wire reads +12V when the door is
open and (-) ground when the door is closed,
it is (+) positive. (most Fords)
•If this wire reads (-) ground when the door
is open and +12V when the door is closed, it
is (-) negative.
Optional part #775 required.
DO NOT USE,
TAPE OFF.
87a
To Dome Light
Circuit
(-) VIOLET
FROM 18-pin
wire
harness.
YELLOW
BLACK
WHITE
BLUE
RED
POSiTIVE DOME LIGHT SUPERVISION
+12 VOLT FUSED
AT 20 AMPS
Optional part #775 required.
DO NOT USE,
TAPE OFF.
87a
To Dome Light
Circuit
+12 VOLT
FUSED AT
5 AMPS
(-) VIOLET
FROM 18-pin
wire
harness.
YELLOW
BLACK
WHITE
BLUE
RED
NEGATIVE DOME LIGHT SUPERVISION
Ground 8
“Type A” - Positive type door locks used on most
GM, some Chrysler vehicles.
GREEN/BLACK
LOCK
UNLOCK
BROWN/BLACK
CONNECTING DOOR LOCKS (Optional)
CONNECTING “TYPE A LOCKS”
•If your vehicle has a “Type A” door locking system,
connect the BROWN WITH BLACK STRIPE wire from the
18-pin harness to the door lock wire. Connect the
GREEN WITH BLACK STRIPE wire to the unlock wire.
See diagram below.
Testing Switch Wire and Motor Wires
Before connecting, you must now determine which wire is the switch wire and which is the motor wire. Cut both
the lock and unlock wires in half. Start with both of the lock wires by placing the clip end of your test
light to ground, hold the door lock switch in the lock position, make sure you are using the master switch
(usually on the driver’s door) and probe both lock wires looking for voltage. The wire that illuminates the
test light, mark as the switch wire, the wire that shows no voltage, mark as the motor wire. Repeat the procedure
for the unlock wire. When connecting the lock and unlock wires to the #778 relay harness, make sure you connect
the switch wire to the RED wire or pin #87A and the motor wire to the BLUE wire or pin #30. Be sure to connect
the lock wires to the lock relay, and the unlock wires to the unlock relay, you may need to mark these relays
before you start.