Combination Switch: Description and Operation
MULTI-FUNCTION SWITCHDESCRIPTION
The multi-function switch (1) is located on the steering column, just below the steering wheel. The only visible components of the multi-function switch are the right (2) and left control stalks (3). One stalk extends through the steering column shrouds on each side of the steering column. The remainder of the switch including its mounting provisions, its electrical connection, and the turn signal cancel actuator (4) are concealed beneath the shrouds.
The switch housing and controls are constructed of molded black plastic. A saddle-like formation in the center of the lower switch housing straddles the steering column tube just below the column lock housing, and two locating posts integral to the lower surface of the switch housing engage two holes in the forward-facing side of the lock housing. Also several integral ledge-like locating tabs on the switch housing are supported and located by several mating points on the column lock housing. When the steering column shrouds are installed on the column, mounting tabs on the switch housing and the clockspring are clamped to the lock housing by the same two screws that secure the column shrouds to the column and each other.
There are several versions of the multi-function switch to support both optional equipment and regulatory equipment that is required only in certain markets. Each multi-function switch control stalk has both white nomenclature and International Control and Display Symbol graphics applied to it, which clearly identify its many functions. Each control stalk has a control knob (5 and 8) on its end with a flattened face to allow it to be easily rotated. On vehicles equipped with optional front fog lamps, the knob on the end of left control stalk can also be pulled outward to select those lamps.
Each control stalk also features a knurled control ring (6 and 7) located just below the control knob. The left control stalk is dedicated to providing driver controls for the interior and exterior lighting systems, while the right control stalk is dedicated to providing driver controls for the front and rear wiper systems.
Two integral connector receptacles on the multi-function switch housing connect the switch to the vehicle electrical system through two dedicated take outs and connectors of the instrument panel wire harness. The left connector receptacle contains nine terminal pins for the lighting control circuits of the switch, while the right connector receptacle contains six terminal pins for the wiper control circuits of the switch.
The multi-function switch cannot be adjusted or repaired. If any function of the switch is ineffective, or if the switch is damaged, the entire switch must be replaced as a unit.
LEFT CONTROL STALK
The left (lighting) control stalk of the multi-function switch supports the following functions and features:
- Front Fog Lamps - For vehicles so equipped, the left multi-function switch control knob provides detent switching for the optional front fog lamps.
- Headlamps - The left multi-function switch control knob provides detent switching for the headlamps.
- Headlamp Beam Selection - The left multi-function switch control stalk provides detent switching for selection of the headlamp high or low beams.
- Headlamp Optical Horn - The left multi-function switch control stalk 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.
- Interior Lamps Defeat - The left multi-function switch control ring provides detent switching to defeat the illumination of all interior courtesy lamps when a door, the rear flip-up glass, or the tailgate are opened.
- Interior Lamps On - The left multi-function switch control ring provides detent switching to simultaneously illuminate all interior courtesy lamps. Panel Lamps Dimming - The left multi-function switch control ring provides simultaneous adjustable control of the illumination intensity of all instrument panel lighting at one of six available illumination intensity levels.
- Parade Mode - The left multi-function switch control ring provides detent switching for a parade mode that maximizes the illumination intensity of all instrument panel lighting for visibility when driving in daylight with the exterior lamps turned on.
- Park Lamps - The left multi-function switch control knob provides detent switching for the park lamps.
- Rear Fog Lamps - For vehicles so equipped, the left multi-function switch control knob provides detent switching for the optional rear fog lamps. Rear fog lamps are optional only for vehicles manufactured for certain markets, where they are required.
- Turn Signal Control - The left multi-function switch control stalk provides both momentary non-detent switching and detent switching with automatic cancellation for both the left and right turn signal lamps.
RIGHT CONTROL STALK
The right (wiper) control stalk of the multi-function switch supports the following functions and features:
- Continuous Front Wipe Modes - The right multi-function switch control knob provides two continuous front wipe switch positions, low speed or high speed.
- Continuous Rear Wipe Mode - The right multi-function switch control ring provides one continuous rear wipe switch position.
- Front Washer Mode - The right multi-function switch control stalk provides front washer system operation.
- Front Wipe-After-Wash Mode - The right multi-function switch control stalk provides a wipe-after-wash mode.
- Front Wiper Mist Mode - The right multi-function switch control stalk provides a front wiper system mist mode.
- Intermittent Front Wipe Mode - The right multi-function switch control knob provides an intermittent front wipe mode with five delay interval positions.
- Intermittent Rear Wipe Mode - The right multi-function switch control ring provides one fixed interval intermittent rear wipe mode switch position.
- Rear Washer Mode - The right multi-function switch control ring provides rear washer system operation.
OPERATION
The multi-function switch uses a combination of resistor multiplexed and conventionally switched outputs to control the many functions and features it provides. The switch receives battery voltage on a fused ignition switch output (run-acc) circuit from a fuse in the Junction Block (JB) whenever the ignition switch is in the On or Accessory positions. The switch receives a path to ground at all times through a ground stud on the driver side instrument panel end bracket near the Junction Block (JB).
The multi-function switch can be diagnosed using conventional diagnostic tools and methods. However, proper testing of the multiplexed inputs to the Body Control Module (BCM) requires the use of a diagnostic scan tool.
Following are brief descriptions of how each of the two multi-function switch control stalks operate to control the functions and features they provide.
LEFT CONTROL STALK
The left (lighting) control stalk of the multi-function switch operates as follows:
- Front Fog Lamps - For vehicles so equipped, the control knob on the end of the multi-function switch left (lighting) control stalk is pulled outward to activate the optional front fog lamps. The control knob is mechanically keyed so that it cannot be pulled outward unless it is first rotated to turn On the exterior lighting. The multi-function switch provides a resistor multiplexed output to the Body Control Module (BCM) on a fog lamp switch sense circuit, and the BCM responds by energizing or de-energizing the front fog lamp relay in the Junction Block (JB).
- Headlamps - The control knob on the end of the multi-function switch left (lighting) control stalk is rotated forward to its second detent position to activate the headlamps. The multi-function switch provides a resistor multiplexed output to the Body Control Module (BCM) on a headlamp switch sense circuit, and the BCM responds by energizing or de-energizing the selected low or high beam relay (Daytime Running Lamp relay in Canadian vehicles) in the Junction Block (JB).
- Headlamp Beam Selection - The left (lighting) control stalk of the multi-function switch is pulled towards the steering wheel past a detent to actuate the integral beam select switch circuitry. Each time the control stalk is activated in this manner, the opposite headlamp beam from what is currently selected will be energized. The multi-function switch provides a ground output to the Body Control Module (BCM) on a high beam switch sense circuit, and the BCM responds by energizing or de-energizing the selected low or high beam relay (Daytime Running Lamp relay in Canadian vehicles) in the Junction Block (JB).
- Headlamp Optical Horn - The left (lighting) control stalk of the multi-function switch is pulled towards the steering wheel to just before a detent, to momentarily activate the headlamp optical horn feature. The high beams will remain illuminated until the control stalk is released. The multi-function switch provides a ground output on a high beam relay control circuit to energize the headlamp high beam relay (Daytime Running Lamp relay in Canadian vehicles) in the Junction Block (JB).
- Interior Lamps Defeat - The control ring on the multi-function switch left (lighting) control stalk is rotated to a full rearward (clockwise) detent to defeat the illumination of all interior courtesy lamps. The multi-function switch provides a resistor multiplexed output to the Body Control Module (BCM) on a panel lamps dimmer switch circuit, and the BCM responds by de-energizing its internal courtesy lamp driver circuit.
- Interior Lamps On - The control ring on the multi-function switch left (lighting) control stalk is rotated to a full forward detent to illuminate all interior courtesy lamps. The multi-function switch provides a resistor multiplexed output to the Body Control Module (BCM) on a panel lamps dimmer switch circuit, and the BCM responds by energizing its internal courtesy lamp driver circuit.
- Panel Lamps Dimming - The control ring on the multi-function switch left (lighting) control stalk is rotated to one of six minor intermediate detents to simultaneously select the desired illumination intensity of all adjustable instrument panel and instrument cluster lighting. The control ring is rotated rearward to dim, or forward to brighten. The multi-function switch provides a resistor multiplexed output to the Body Control Module (BCM) on a panel lamps dimmer switch circuit, and the BCM responds by sending an electronic panel lamps dimming level message to the ElectroMechanical Instrument Cluster (EMIC) over the Programmable Communications Interface (PCI) data bus. The EMIC electronic circuitry then provides the proper PWM output to the cluster illumination lamps and the Vacuum Florescent Display (VFD) on the EMIC circuit board, and provides a matching Pulse Width Modulation (PWM) output on the hard wired fused panel lamps dimmer switch signal circuit.
- Parade Mode - The control ring on the multi-function switch left (lighting) control stalk is rotated to an intermediate detent that is one detent rearward from the full forward detent to select the Parade mode. The multifunction switch provides a resistor multiplexed output to the Body Control Module (BCM) on a panel lamps dimmer switch circuit, and the BCM responds by sending an electronic panel lamps dimming level message to the ElectroMechanical Instrument Cluster (EMIC) over the Programmable Communications Interface (PCI) data bus. The EMIC electronic circuitry then provides the proper PWM output to the cluster illumination lamps and the VFD on the EMIC circuit board, and provides a matching PWM output on the hard wired fused panel lamps dimmer switch signal circuit to illuminate all lamps at full (daylight) intensity with the exterior lamps turned On.
- Park Lamps - The control knob on the end of the multi-function switch left (lighting) control stalk is rotated forward to its first detent from the Off position to activate the park lamps. The multi-function switch provides a resistor multiplexed output to the Body Control Module (BCM) on a headlamp switch sense circuit, and the BCM responds by energizing or de-energizing the park lamp relay in the Junction Block (JB).
- Rear Fog Lamps - For vehicles so equipped, the control knob on the end of the multi-function switch left (lighting) control stalk is rotated forward to its third detent position to activate the rear fog lamps. The multifunction switch provides a resistor multiplexed output to the Body Control Module (BCM) on a headlamp switch sense circuit, and the BCM responds by energizing or de-energizing the rear fog lamp relay in the Junction Block (JB). Rear fog lamps are optional only for vehicles manufactured for markets, where they are required.
- Turn Signal Control - The left (lighting) control stalk of the multi-function switch is moved upward to activate the right turn signal circuitry, and downward to activate the left turn signal circuitry. 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 is integral to the clockspring and rotates with the steering wheel. The cam lobe contacts the cancel actuator when it is extended from the multifunction switch. When the steering wheel is rotated during a turning maneuver, the turn signal cancel cam lobe will contact the turn signal cancel actuator. The cancel actuator latches against the cancel cam rotation in the direction opposite that which is signaled. If the left turn signal detent is selected, the lobe 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. When a turn signal is activated, the multi-function switch provides a ground output on a right or left turn switch sense circuit to the combination flasher circuitry within the hazard switch, and the combination flasher flashes the turn signal lamps.
RIGHT CONTROL STALK
The right (wiper) control stalk of the multi-function switch operates as follows:
- Continuous Front Wipe Modes - The control knob on the end of the multi-function switch right (wiper) control stalk is rotated to an intermediate detent that is one detent rearward from the full forward detent to select the low speed continuous front wiper mode, or to its full forward detent to select the high speed continuous front wiper mode. The multi-function switch provides a resistor multiplexed output to the Body Control Module (BCM) on a front wiper switch circuit, and the BCM responds by energizing the wiper on/off relay in the Power Distribution Center (PDC) for the front low speed continuous wipe mode, or the wiper on/off relay and the wiper high/low relay in the PDC for the front high speed continuous wipe mode as required.
- Continuous Rear Wipe Mode - The control ring on the multi-function switch right (wiper) control stalk is rotated to the most forward detent to select the continuous rear wiper mode. The multi-function switch provides a battery voltage output to the rear wiper motor on a rear wiper on driver circuit to signal the rear wiper motor to operate in the continuous wipe mode.
- Front Washer Mode - The right (wiper) control stalk of the multi-function switch is pulled towards the steering wheel to momentarily activate the washer pump in the front washer mode. The washer pump will continue to operate in the front washer mode until the control stalk is released. The multi-function switch provides a ground output on a washer pump sense circuit, and battery voltage on a washer pump driver circuit to energize the washer pump in the front washer mode.
- Front Wiper Mist Mode - The right (wiper) control stalk of the multi-function switch is pushed towards the floor to momentarily activate the front wiper motor in the mist mode. The front wiper motor will continue to operate in the mist mode until the control stalk is released. The multi-function switch provides a resistor multiplexed output to the Body Control Module (BCM) on a front wiper switch circuit, and the BCM responds by energizing the wiper on/off relay in the Power Distribution Center (PDC) to operate the front wiper motor momentarily at low speed to provide the front wiper mist mode.
- Intermittent Front Wipe Mode - The control knob on the end of the multi-function switch right (wiper) control stalk is rotated to one of five minor intermediate detents to select the desired intermittent front wipe delay interval. The control knob is rotated rearward to increase the delay, or forward to decrease the delay. The multi-function switch provides a resistor multiplexed output to the Body Control Module (BCM) on a front wiper switch circuit, and the BCM responds by energizing the wiper on/off relay in the Power Distribution Center (PDC) to operate the front wiper motor at the selected delay intervals.
- Intermittent Rear Wipe Mode - The control ring on the multi-function switch right (wiper) control stalk is rotated to the center detent to select the intermittent rear wiper mode. The multi-function switch provides a battery voltage output to the rear wiper motor on a rear wiper intermittent driver circuit to signal the rear wiper motor to operate in the intermittent wipe mode.
- Rear Washer Mode - The control ring on the multi-function switch right (wiper) control stalk is rotated to either the full forward or full rearward momentary positions to activate the washer pump in the rear washer mode. The washer pump will continue to operate in the rear washer mode until the control ring is released. The multi-function switch provides a ground output on a washer pump driver circuit, and battery voltage on a washer pump sense circuit to energize the washer pump in the rear washer mode.