GM Service Manual Online
For 1990-2009 cars only

Turn Lamps

Voltage is applied through the TURN fuse and the turn/hazard flasher when the ignition switch is in the following positions:

    • RUN
    • BULB TEST
    • START

The voltage travels to the contact in the hazard switch. The hazard switch is located in the turn/hazard-headlamp switch assembly. This contact is normally closed.

When the left turn signal is turned on, voltage is applied to the following components.

    • The left turn indicator
    • The left front park/turn lamp circuit 14
    • The left rear turn lamp circuit 18

The turn lamps turn on immediately. The current flow heats up the timing element. The timing element is located in the turn/hazard flasher. The timing element repeatedly opens and closes the circuit. This action causes the turn lamps to begin flashing.

The voltage that is applied to the left front park/turn lamp is also applied to the left front marker lamp. If the headlamp switch is in the OFF position, the left front marker lamp will find a path to ground through one of the following lamps. The following lamps provide low resistance paths to ground:

    • The right front marker lamp
    • The right turn indicator
    • The right front park/turn lamps
    • The left front park/turn lamps

The left front marker lamp flashes with the turn lamps. The voltage drop across the marker lamp is much higher than the voltage drop across the other lamps. The lamps that are used for the ground path will not flash.

When the headlamp switch is in either the PARK or HEAD positions, voltage is applied through the following components:

    • The EXT LP fuse
    • The marker lamps
    • The park lamps

When the left turn signal is turned on, the left marker lamp will have voltage at both connections. The left marker lamp does not light. When the turn/hazard flasher stops the voltage to the turn lamps, the marker lamp is grounded through the turn lamp. The marker lamp does not go on. The left front marker lamp flashes in the following manner:

    • The left front marker lamp flashes on when the turn filament of the left front park/turn lamp goes off.
    • The left front marker lamp flashes off when the turn filament of the left front park/turn lamp goes on.

Voltage is applied to the right lamps in the same manner, when the right turn signal is turned on.

Hazard Lamps

Voltage is applied at all times through the following components to the normally open contact of the hazard switch in the turn/hazard-headlamp switch assembly:

    • The STOP HAZ fuse
    • The turn/hazard flasher

When the hazard switch is turned on, voltage is applied to the following components:

    • The front turn lamps
    • The rear turn lamps

The following lamps flash on and off:

    • All of the turn lamps
    • Both of the turn indicators

The front marker lamps flash with the hazard lamps on, just as the front marker lamps flash when the turn lamps are on. If the headlamp switch is in the OFF position, the front marker lamps flash on when the hazard lamps are on. The front marker lights will flash on when the hazard lamps are on if the headlamp switch is in one of the following positions:

    • PARK
    • HEAD

When the hazard lamps are on, the following conditions apply:

    • The turn circuit is always open.
    • The turn/hazard flasher controls the lamp.

Park/Marker Lamps

Voltage is applied through the EXT LP fuse, to the headlamp switch at all times. Voltage is applied to the park lamps and the marker lamps when the headlamp switch is in the following positions:

    • PARK
    • HEAD

The front marker lamps are grounded through the turn filament of the respective front park/turn lamp. The front marker lamps light as a result.

Stop Lamps

Voltage is applied through the STOP HAZ fuse to the brake switch at all times. When the brake pedal is depressed, the brake switch closes. This action applies voltage through the turn/hazard-headlamp switch assembly to the following lamps:

    • The high mounted stop lamp assembly
    • The left tail/stop-turn lamps
    • The right tail/stop-turn lamps

Tail/Rear Marker/License Lamps

Voltage is applied through the EXT LP fuse to the headlamp switch at all times. Voltage is applied to all of the lamps in this circuit when the headlamp switch is in one of the following positions:

    • PARK
    • HEAD

On the Pontiac coupe, voltage for the license lamps is supplied through the HVAC fuse. The license lamps are lit when the ignition switch is in the RUN position.