Hazard Warning Switch: Description and Operation

Multi-Function Switch:

MULTI-FUNCTION SWITCH
The multi-function switch is secured with two screws to the left side of the upper steering column housing at the top of the steering column, just below the steering wheel. The only visible parts of the multi-function switch are the control stalk that extends through a dedicated opening in the left side of the upper steering column shrouds, and the hazard warning switch push button that protrudes through an opening in the upper steering column shroud on the top of the steering column. The remainder of the switch, its mounting provisions, and its electrical connections are all concealed beneath the steering column shrouds. The multi-function switch control stalk has both nomenclature and International Control and Display Symbol graphics applied to it, which identify its many functions. An International Control and Display Symbol icon for "Hazard Warning" is applied to the top of the hazard warning switch push button.

The switch housing and its controls are constructed of molded black plastic. A single connector receptacle with up to twenty-four terminals is located on the back of the switch housing and connects the switch to the vehicle electrical system through a take out and connector of the instrument panel wire harness. The connector receptacle also has a threaded receptacle for a screw, which secures the wire harness connector to the switch connector receptacle.

The multi-function switch supports the following functions and features:
- Continuous Wipe Modes - The control knob of the multi-function switch provides two continuous wipe switch positions, low speed or high speed.
- Hazard Warning Control - The internal circuitry and hardware of the multi-function switch provide detent switching for activation and deactivation of the hazard warning system.
- Headlamp Beam Selection - The internal circuitry and hardware of the multi-function switch provide detent switching for selection of the headlamp high or low beams.
- Headlamp Optical Horn - The internal circuitry and hardware of the multi-function switch includes momentary switching of the headlamp high beam circuits to provide an optical horn feature (sometimes referred to as flash-to-pass), which allows the vehicle operator to momentarily flash the headlamp high beams as an optical signalling device.
- Intermittent Wipe Mode - The control knob of the multi-function switch provides an intermittent wipe mode with multiple delay interval positions.
- Turn Signal Control - The internal circuitry and hardware of the multi-function switch provide both momentary non-detent switching and detent switching with automatic cancellation for both the left and right turn signals.
- Washer Mode - A button on the end of the control stalk of the multi-function switch provides washer system operation when the button is depressed towards the steering column.

The multi-function switch cannot be adjusted or repaired. If any function of the switch is faulty, or if the switch is damaged, the entire switch unit must be replaced.

The multi-function switch uses conventionally switched outputs and a variable resistor to control the many functions and features it provides using hard wired circuitry. The switch is grounded at all times through a single wire take out with an eyelet terminal connector of the instrument panel wire harness that is secured by a nut to a ground stud located on the instrument panel armature, just above and to the left of the glove box opening. When the ignition switch is in the Accessory or ON positions, battery current from a fuse in the Junction Block (JB) is provided through a fused ignition switch output (RUN/ACC) circuit. Following are descriptions of the how the multi-function switch operates to control the many functions and features it provides:
- Continuous Wipe Modes - When the control knob of the multi-function switch is rotated to the High or Low positions, the circuitry within the switch provides a battery current output directly to the high or low speed brush of the wiper motor. When the control knob is in the OFF position, the circuitry within the switch connects the output of the wiper motor park switch to the low speed brush of the wiper motor.
- Hazard Warning Control - The hazard warning push button is pushed down to unlatch the switch and activate the hazard warning system, and pushed down again to latch the switch and turn the system OFF. When the hazard warning switch is latched (hazard warning OFF), the push button will be in a lowered position on the top of the steering column shroud; and, when the hazard warning switch is unlatched (hazard warning ON), the push button will be in a raised position. The multi-function switch hazard warning circuitry simultaneously provides a signal to the hazard warning sense of the combination flasher to activate or deactivate the flasher output, and directs the output of the flasher to the hazard warning lamps.
- Headlamp Beam Selection - The multi-function switch control stalk is pulled towards the steering wheel past a detent, then released to actuate the headlamp beam selection switch. Each time the control stalk is actuated in this manner, the opposite headlamp mode from what is currently selected will be activated. The internal circuitry of the headlamp beam selection switch directs the output of the headlamp switch through hard wired circuitry to activate the selected headlamp beam.
- Headlamp Optical Horn - The left multi-function switch control stalk is pulled towards the steering wheel to just before a detent, to momentarily activate the headlamp high beams. The high beams will remain illuminated until the control stalk is released. The internal circuitry of the headlamp beam selection switch provides a momentary ground path to the headlamp high beams.
- Intermittent Wipe Mode - When the multi-function switch control knob is rotated to the Delay position, the circuitry within the switch connects the output of the wiper motor relay to the low speed brush of the wiper motor and provides a battery current signal to the Central Timer Module (CTM). If the Delay mode is selected, the control knob can then be rotated to multiple minor detent positions, which actuates a variable resistor within the switch and provides a hard wired output to the CTM that signals the desired delay interval for the intermittent wiper feature.
- Turn Signal Control - The multi-function switch control stalk actuates the turn signal switch. When the control stalk is moved in the upward direction, the right turn signal circuitry is activated; and, when the control stalk is moved in the downward direction, the left turn signal circuitry is activated. The multi-function switch turn signal circuitry simultaneously provides a signal to the turn signal sense of the combination flasher to activate or deactivate the flasher output, and directs the output of the flasher to the proper turn signal lamps. The turn signal 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 left multi-function switch control stalk is released. When the control stalk is moved to a turn signal switch detent position, the cancel actuator extends toward the center of the steering column. A turn signal cancel cam that is integral to the clockspring mechanism rotates with the steering wheel and the cam lobes contact the cancel actuator when it is extended from the multi-function switch. When the steering wheel is rotated during a turning maneuver, one of the two turn signal cancel cam lobes will contact the turn signal cancel actuator. The cancel actuator latches against the cancel cam rotation in the direction opposite that which is signaled. In other words, if the left turn signal detent is selected, the lobes of the cancel cam will ratchet past the cancel actuator when the steering wheel is rotated to the left, but will unlatch the cancel actuator as the steering wheel rotates to the right and returns to center, which will cancel the turn signal event and release the control stalk from the detent so it returns to the neutral OFF position.
- Washer Mode - Pushing the button on the end of the multi-function switch control knob towards the steering column provides a battery current output through the momentary single pole, single throw washer switch circuitry to operate the washer pump/ motor and provides a signal to the CTM. If the wipers are not operating when the washer switch is actuated, the CTM will operate the wiper motor for as long as the washer switch is depressed plus about three additional wipe cycles. If the wipers are operating in the intermittent mode when the washer switch is actuated, the CTM will operate the wiper motor at a fixed low speed for as long as the washer switch is depressed plus about three additional wipe cycles before the wipers return to the selected intermittent wipe interval.