Daytime Running Lamp Control Unit: Description and Operation

Combination Flasher -- With Daytime Running Lamps (DRL)

Combination Flasher Location:

SYSTEM OPERATION
The turn signals are actuated with a lever on the left side of the steering column just ahead of the steering wheel. The signals are automatically turned off by a canceling cam (two lobes molded to the clock- spring mechanism). The cam comes in contact with the cancel actuator on the turn signal (multi-function) switch assembly. Either cam lobe, pushing on the cancel actuator, returns the switch to the OFF position.

Lane change signaling is actuated by applying partial turn signal stalk movement toward the direction desired until the indicator lamps flashes in the instrument cluster. When the switch stalk is released the stalk will spring back into the neutral position turning OFF the turn signal.

With the ignition switch ON and the turn signal switch stalk actuated left or right, current flows through the:
- Combination flasher
- Multi-function switch
- Turn indicator lamp
- Front and rear turn signal bulbs.

A chime will sound after the vehicle has traveled a distance of approximately 0.5 Mile with the turn signal ON.

FLASHER MODULE DESCRIPTION
The Turn Signal/Hazard Warning Flasher is a module providing the vehicle with turn signal and hazard warning functions and has been designed with internal relays to take advantage of low current switching requirements in the vehicle. It is plugged into the Junction Block at position 4, where all wiring associated with its operation is terminated.

The Junction Block is adjacent to and left of the steering column of the vehicle.

To gain access to the flasher, remove the lower steering column cover and knee blocker.

Junction Block Terminal Pins:

FLASHER MODULE OPERATION
The Combination Flasher/DRL is a module providing turn signal, hazard warning, and daytime running light functions, and has been designed with internal relays to take advantage of low current switching requirements in the vehicle. It is plugged into the junction block at positions 3 and 4 where all wiring associated with its operation is terminated. The Junction Block is adjacent to and left of the steering column of the vehicle. To gain access to the device, remove the lower steering column cover and knee blocker.

The combination flasher/DRL may be operated in its hazard warning mode either with or without the ignition circuit being active. However, in order to operate in the turn signal mode or the DRL mode, the ignition circuit must be completed to the module.

While the combination flasher portion is idle, there is no current drawn through the module. The device does not become active in the turn signal or hazard warning modes until a signal ground circuit is supplied to either of the turn signal inputs or the hazard warning input. With the ignition OFF, there is no current drawn through the module.

While the ignition is ON, the front turn signal filaments are illuminated steadily thus providing the DRL function. The DRL function may be inhibited by applying a signal ground input from either the park brake circuit or the headlamp relay activation circuit.

Typical flash rate for the flasher is 90 flashes per minute. When a lamp is burnt out for a given side of the vehicle or a wire is open to a lamp, the flash rate will increase to 180 flashes per minute when in the turn signal mode. When in the hazard warning signal mode the flash rate remains at 90 flashes per minute.

Turn signal inputs that actuate the flasher are low current grounds, each could draw a maximum of 300 mA, and are provided to the flasher through the Junction Block from the multi-function switch that is mounted to the steering column. The hazard warning signal input is a low current ground that could draw a maximum of 600 mA. through the multi-function switch.

Electronic Combination Flasher With DRL Circuit:

Junction Block Terminal Call-Out With DRL:

CIRCUIT OPERATION
The battery input (Pin 1), is brought into the Junction Block through the Electrical Distribution Wiring (EDW) harness through. It originates under the hood in the Power Distribution Center (PDC) through a 20 ampere fuse at position 15 (5th position from the upper end) and labeled HAZARD. This circuit (L09) is the only power feed to the combination-flasher/DRL.

The ignition input of Pin 6, only senses that the ignition circuit is ON and does not supply current to the module in a way that would power the system. This RUN/START circuit is brought into the junction block to a 10 ampere fuse labeled TS BU LMP at the bottom right side. The circuit designation out of the fuse is A22D.

This circuit feeds the combo-flasher and the following systems with Ignition voltage if the vehicle is so equipped:
- Back-Up Lamps
- Electrochromic Inside Rear view Mirror
- A/C Control Head
- Mini-Trip Computer
- ABS Module
- Front Blower Relay Coil
- Rear Blower Relay Coil
- AWD Solenoids
- Rear Window Defogger (EBL) Relay Coil

The ignition input to the combo-flasher will draw typically 5 mA of current while active.