Seat Temperature Switch: Description and Operation

Fig.1 Heated Seat Switch:

LEFT HEATED SEAT SWITCH
Two heated seat switches, one each for the driver side and passenger side front seats, are mounted in a single switch bezel located on the center floor console behind the gearshift selector lever. On models with the heated seat system option, the heated seat switch bezel replaces the standard equipment ash receiver on the center floor console, and an available optional ash receiver is installed in one of the cup holders. The two switches are snapped into the mounting holes of the heated seat switch bezel, and the switch and bezel assembly snaps into the mounting hole of the center floor console. The two switches are identical in appearance and construction, but the power seat wire harness connector insulators for the heated seat switches are color-coded (red is for the left seat control, and blue is for the right) to ensure proper electrical connection.

Each heated seat switch is a single pole, double throw, resistor-multiplexed, rocker-type switch with a center neutral position, and momentary Lo and Hi positions. Each switch has two amber Light-Emitting Diode (LED) indicator lamps, which illuminate to indicate the selected Lo or Hi heating mode. Each switch also has LED illumination lamps that illuminate a small heated seat icon in the center of the switch rocker and the Lo/Hi nomenclature on the opposite ends of the switch rocker anytime the ignition switch is in the ON position. The switch illumination lamps provide improved switch identification, visibility, and ease of use. The heated seat switches cannot be adjusted or repaired. If either switch or any of its LED lamps is damaged or faulty, the individual switch unit must be replaced.

The heated seat switches operate on battery current received through a fuse in the Junction Block (JB) on a fused ignition switch output (run-acc) circuit so that the heated seats will only operate when the ignition switch is in the ON or Accessory positions. The switches receive a ground feed from a two wire take out and eyelet terminal connector of the power seat wire harness that is secured by a ground screw to the top of the seat crossmember under the right front seat. The three illumination LED lamps within each switch are connected to ground at all times, resulting in the switch being illuminated whenever the ignition switch is in the ON or Accessory positions. The switch also contains three resistor circuits that are connected in parallel with each other to the heated seat module (Seat Heat Interface Module or SHIM) through the driver or passenger seat heater MUX circuit. Each switch resistor circuit has a different resistance value, which allows the heated seat module to continually monitor the state of each switch.

One resistor circuit in each switch is connected in series between the battery current source and the SHIM, while the other two resistor circuits are normally open. Depressing the heated seat switch rocker to its Hi or Lo position momentarily closes one of these two normally open resistor circuits, which provides a voltage request signal to the SHIM to power the heated seat elements of the selected seat. If the heated seat switch is depressed again to a different position (Lo or Hi) than the currently selected state, the SHIM will change states to support the new selection. If a heated seat switch is depressed a second time to the same position as the currently selected state, the SHIM interprets the second input as a request to cancel. The SHIM Will then turn OFF the heated seat elements for that seat.

The indicator lamps in the heated seat switches also receive battery current through the fused ignition switch output (run-acc) circuit whenever the ignition switch is in the ON or Accessory positions. The ground side of each indicator lamp is controlled by a separate driver or passenger seat high or low heat LED driver circuit from the SHIM. When the SHIM sees a Hi or Lo heat request signal from a heated seat switch, it simultaneously pulls the proper LED driver circuit to ground to indicate the current state of that seat heater. Likewise, the SHIM will turn OFF the indicator lamps when a cancel request is received. The SHIM control of the switch indicator lamps also allows the module to provide self-diagnostic feedback to indicate monitored heated seat system faults by flashing the LED indicator lamps in a programmed routine. Refer to Heated Seat System Diagnosis and Testing for more information on this heated seat system self-diagnostic feature.

Fig.3 Heated Seat Switch:

RIGHT HEATED SEAT SWITCH
Two heated seat switches, one each for the driver side and passenger side front seats, are mounted in a single switch bezel located on the center floor console behind the gearshift selector lever. On models with the heated seat system option, the heated seat switch bezel replaces the standard equipment ash receiver on the center floor console, and an available optional ash receiver is installed in one of the cup holders. The two switches are snapped into the mounting holes of the heated seat switch bezel, and the switch and bezel assembly snaps into the mounting hole of the center floor console. The two switches are identical in appearance and construction, but the power seat wire harness connector insulators for the heated seat switches are color-coded (red is for the left seat control, and blue is for the right) to ensure proper electrical connection.

Each heated seat switch is a single pole, double throw, resistor-multiplexed, rocker-type switch with a center neutral position, and momentary Lo and Hi positions. Each switch has two amber Light-Emitting Diode (LED) indicator lamps, which illuminate to indicate the selected Lo or Hi heating mode. Each switch also has LED illumination lamps that illuminate a small heated seat icon in the center of the switch rocker and the Lo/Hi nomenclature on the opposite ends of the switch rocker anytime the ignition switch is in the ON position. The switch illumination lamps provide improved switch identification, visibility, and ease of use. The heated seat switches cannot be adjusted or repaired. If either switch or any of its LED lamps is damaged or faulty, the individual switch unit must be replaced.

The heated seat switches operate on battery current received through a fuse in the Junction Block (JB) on a fused ignition switch output (run-acc) circuit so that the heated seats will only operate when the ignition switch is in the ON or Accessory positions. The switches receive a ground feed from a two wire take out and eyelet terminal connector of the power seat wire harness that is secured by a ground screw to the top of the seat crossmember under the right front seat. The three illumination LED lamps within each switch are connected to ground at all times, resulting in the switch being illuminated whenever the ignition switch is in the ON or Accessory positions. The switch also contains three resistor circuits that are connected in parallel with each other to the heated seat module (Seat Heat Interface Module or SHIM) through the driver or passenger seat heater MUX circuit. Each switch resistor circuit has a different resistance value, which allows the heated seat module to continually monitor the state of each switch.

One resistor circuit in each switch is connected in series between the battery current source and the SHIM, while the other two resistor circuits are normally open. Depressing the heated seat switch rocker to its Hi or Lo position momentarily closes one of these two normally open resistor circuits, which provides a voltage request signal to the SHIM to power the heated seat elements of the selected seat. If the heated seat switch is depressed again to a different position (Lo or Hi) than the currently selected state, the SHIM will change states to support the new selection. If a heated seat switch is depressed a second time to the same position as the currently selected state, the SHIM interprets the second input as a request to cancel. The SHIM will then turn OFF the heated seat elements for that seat.

The indicator lamps in the heated seat switches also receive battery current through the fused ignition switch output (run-acc) circuit whenever the ignition switch is in the ON or Accessory positions. The ground side of each indicator lamp is controlled by a separate driver or passenger seat high or low heat LED driver circuit from the SHIM. When the SHIM sees a Hi or Lo heat request signal from a heated seat switch, it simultaneously pulls the proper LED driver circuit to ground to indicate the current state of that seat heater. Likewise, the SHIM will turn OFF the indicator lamps when a cancel request is received. The SHIM control of the switch indicator lamps also allows the module to provide self-diagnostic feedback to indicate monitored heated seat system faults by flashing the LED indicator lamps in a programmed routine. Refer to Heated Seat System Diagnosis and Testing for more information on this heated seat system self-diagnostic feature.