Turn Signals: Description and Operation
INTRODUCTIONTurn signal and hazard warning systems are standard factory-installed equipment on this model.
Turn Signal System
With the ignition switch in the On or Accessory position, and the multi-function switch control lever moved up (right turn) or down (left turn), the turn signal system is activated. The switch has a detent position in each direction that provides turn signals with automatic cancellation, and an intermediate momentary position in each direction that provides turn signals only until the multi-function switch lever is released.
When the turn signal switch is in a detent position, it is turned off by one of two cancelling cam lobes molded into the hub of the clockspring mechanism. When turning the steering wheel causes one of the cam lobes to contact a cancel actuator in the multi-function switch, the turn signal switch automatically returns to the off position. When the turn signal system is activated, the selected (right or left) turn signal indicator lamp, front park/turn signal lamp, and rear tail/stop/turn signal lamp bulbs will flash.
Following are general descriptions of the major components in the turn signal system. Refer to the owner's manual in the vehicle glove box for more information on the features, use and operation of the turn signal system.
Hazard Warning System
The hazard warning system is activated by a switch button in the multi-function switch. The button is located on the top of the steering column between the steering wheel and the instrument panel. The hazard warning switch button is identified with a double triangle.
The hazard warning system is connected to a nonswitched battery feed so that the system remains functional, regardless of the ignition switch position. Push the switch button in to activate the hazard warning system, and push in on the button again to turn the system off. When the hazard warning system is activated, the right and left turn signal indicators, front park/turn signal lamps, and rear tail/ stop/turn signal lamps will flash.
Following are general descriptions of the major components in the hazard warning system. Refer to the owner's manual in the vehicle glove box for more information on the features, use and operation of the hazard warning system.
SYSTEM OPERATION
Combination Flasher
The combination flasher is a smart relay that functions as both the turn signal system and hazard warning system flasher. The combination flasher contains active electronic Integrated Circuitry (IC) elements. This flasher is designed to handle the current flow requirements of the factory-installed lighting. If supplemental lighting is added to the turn signal lamp circuits, such as when towing a trailer with lights, the combination flasher will automatically try to compensate to keep the flash rate the same.
While the combination flasher has a International Standards Organization (ISO)-type relay terminal configuration or footprint, the internal circuitry is much different. The combination flasher does not use standard ISO-relay inputs or provide ISO-relay type outputs or functions. The combination flasher should never be substituted for an ISO-relay or replaced with an ISO-relay, or else component and vehicle damage may occur.
The combination flasher has five blade-type terminals intended for the following inputs and outputs: Battery B+, Ignition B+, Ground, Turn Signal circuit, and Hazard Warning circuit. Constant battery voltage and ground are supplied to the flasher so that it can perform the hazard warning function, and ignition switched battery voltage is supplied for the turn signal function.
Combination Flasher - Typical:
The IC within the combination flasher contains the logic that controls the flasher operation and the flash rate. Pin 6 of the IC receives a sense voltage from the hazard warning portion of the multi-function switch. When the hazard switch is turned on, the "hazard on sense" voltage will become low due to the circuit being grounded through the turn signal bulbs. This low voltage sense signals the IC to energize the flash control Positive-Negative-Positive (PNP) transistor at a pre-calibrated flash rate or frequency. Each time the PNP transistor energizes the hazard warning circuit, the pin 6 "hazard on sense" voltage will become high and the IC signals the PNP transistor to de-energize the circuit. This cycling will continue until the hazard warning switch is turned off.
Likewise, pin 8 of the IC receives a sense voltage from the turn signal portion of the multi-function switch. When the left or right turn signal is turned on, the "turn signal on sense" voltage will become low due to the circuit being grounded through the turn signal bulbs. This low voltage sense signals the IC to energize the flash control PNP transistor at a precalibrated flash rate or frequency Each time the PNP transistor energizes the turn signal circuit, the pin 8 "turn signal on sense" voltage will become high and the IC signals the PNP transistor to de-energize the circuit. This cycling will continue until the right or left turn signal is turned off.
A special design feature of the combination flasher allows it to "sense" that a turn signal circuit or bulb is not operating, and provide the driver an indication of the condition by flashing the remaining bulbs in the affected circuit at a higher rate (120 flashes-per-minute or higher). Conventional flashers either continue flashing at their typical rate (heavy-duty type), or discontinue flashing the affected circuit entirely (standard-duty type). During turn signal operation, the combination flasher IC compares normal battery voltage input on pin 2 with the shunt resistor voltage input on pin 7. If the IC "senses" that the voltage difference between pin 2 and pin 7 is different than the pre-calibrated value of the IC, it will increase the rate at which it signals the PNP transistor to energize the pin 1 output. Thus, the inoperative half (left or right side) of the turn signal circuit will flash faster.
Because of the active electronic elements within the combination flasher, it cannot be tested with conventional automotive electrical test equipment. If the combination flasher is believed to be faulty, test the turn signal and hazard warning system circuits as described. Then replace the combination flasher with a known good unit to confirm system operation.
The combination flasher cannot be repaired and, if faulty or damaged, it must be replaced.
Turn Signal Switch And Hazard Warning Switch
Multi-Function Switch:
The turn signal and hazard warning switches are contained in the multi-function switch assembly. The multi-function switch assembly is secured to the left side of the steering column. A switch stalk that extends from the left side of the steering column is moved up or down to activate the right or left turn signals, respectively. A latching push-button that extends upward from the multi-function switch and through the top of the upper steering column shroud is used to control the hazard warning system.
The multi-function switch contains circuitry for the following functions:
- Turn signals
- Hazard warning
- Headlamp beam selection
- Headlamp optical horn
- Windshield wipers
- Windshield washers.
The information contained addresses only the switch functions for the turn signal and hazard warning systems. However, the multi-function switch cannot be repaired. If any function of the multi-function switch is faulty, or if the switch is damaged, the entire switch assembly must be replaced.
Turn Signal Indicator Lamp
The turn signal indicator lamps are located in the instrument cluster. They flash with the exterior turn signal lamps to give the driver a visual indication that a turn signal or the hazard warning system is operating. Refer to Turn Signal Indicator Lamp in Instrument Panel Systems for diagnosis or service of these lamps.
Turn Signal Lamp
The exterior lamps in the turn signal and hazard warning circuits include the front park/turn signal, and the rear tail/stop/turn signal. Refer to Exterior Lamps in Lamps for diagnosis and service of the turn signal lamps.