Pontiac Fiero 1988 Service Manual page 1138

POWER DOOR LOCKS: A U 3
(Continued from facing page)
® If all the results are correct, check the TAN
(294) and GRY (295) wires for opens (see
schematic). If OK, do Test A.
1. Check the LT BLU (195) wire for an open
(see schematic). If the wire is good, do Test
B.
2. Check the BLK (194) wire for an open (see
schematic). If the wire is good, do Test B.
3. Replace the Door Lock Relay Assembly.
CIRCUIT
O P E R A T I O N
When a Door Lock Switch is activated in the
Power Door Lock system, all of the doors will
lock or unlock in unison. Each lock can also be
operated manually from the locking post. The
locks are operated by reversible motors that re-
ceive voltage from two relays in the Door Lock
Relay Assembly. These relays operate to turn the
motors on by applying a voltage to one of the
terminals and a ground to the other terminal.
When either Door Lock Switch is moved to the
LOCK position, it completes the circuit to the
coil of the Door Lock Relay Assembly. The lock
relay is energized. The contact for the lock relay
closes, and is connected to battery voltage
through the ORN/BLK wire. Voltage is then ap-
plied to the GRY wire and the Door Lock
Motors. The motors are grounded by the TAN
wire from the other terminal of the motor
through the contact for the unlock relay. The
motor in each door runs to operate the Door
Locks. When the Door Lock Switch is released,
the lock relay contact returns to ground and the
motors turn off.
A similar action occurs with the unlock relay
when it is energized by either of the Door Lock
Switches closing to the UNLOCK position. Now
the TAN wires to the motors carry battery volt-
age and the GRY wires are grounded. The polar-
ity of the voltage to the motors has been
reversed. The motors run in the opposite direc-
tion to unlock the doors.
The Door Lock Switches are usually closed for
just a moment. If they are held closed, a circuit
breaker in each motor will open to protect
against damage. The circuit breakers close auto-
matically when they cool off.