Sebring Sedan V6-2.7L VIN R (2004)
Seat Heater: Description and Operation
Heated Seat Element
Vehicles equipped with the optional heated seat system have two sets of electrically operated heating element grids located in each outboard seating
position of the front seat, one set for the seat cushion and the other set for the seat back. Each of the heated seat element grids consists of a single length
of resistor wire that is routed in a zigzag pattern and captured between the leather trim cover and the foam rubber backing on the underside of its
respective seat cushion trim cover and seat back trim cover assembly. Short pigtail wires with connectors are soldered to each end of each resistor wire
element grid, which connect all of the element grids for each seating position to each other in series with the heated seat module through the seat wire
harness.
One temperature sensor is used for each outboard seating position of the front seat, and it is located in the center insert area of the seat cushion cover.
The heated seat sensors and their pigtail wires are also captured between the leather trim cover and the foam rubber backing on the underside of their
respective seat cushion trim cover assemblies. The heated seat sensors are Negative Thermal Coefficient (NTC) thermistors. The sensors for both front
seats receive a voltage feed from a single output of the heated seat module, but the module receives individual sensor inputs from the driver side and
passenger side sensors.
The heated seat elements and sensors cannot be repaired. If damaged or faulty, the elements and sensors must be replaced.
One end of the heated seat element resistor wire is connected to a ground feed at all times through a splice in the heated seat module ground circuit.
Battery current is directed to the other end of the heated seat element resistor wire by the energized N-channel Field Effect Transistor (N-FET) located
within the heated seat module. The heated seat module will energize the N-FET only when the heated seat switch is in one of the six positions and the
heated seat sensor indicates that the seat cushion surface temperature is below the selected (Low or High) temperature set point. As electrical current
passes through the heating element grid, the resistance of the wire used in the element disperses some of that electrical current in the form of heat. The
heat produced by the heated seat element grid then radiates through the underside of the seat cushion and seat back trim covers, warming the seat cover
and its occupant.
The resistance of the heated seat sensor increases and decreases as the surface temperature of the seat cushion cover changes. The heated seat module
supplies each sensor with a voltage feed, then detects the sensor resistance by monitoring the voltage of the separate sensor return circuits. The heated
seat module compares the heated seat sensor resistance (seat cushion surface temperature) with the heated seat switch resistance (Low or High set point)
to determine when the heated seat element grids need to be cycled on or off in order to maintain the selected temperature set point.
A low voltage cut-out relay controls the 12v battery feed to the heated seat elements. When the system voltage is above 12.2 volts the relay will supply
voltage to the elements. When the PCM senses low system voltage, below 11.7 volts, a message will be sent to the BCM to turn off the low voltage relay
to prevent battery discharge during normal operation. The power will be restored when the system voltage rises above 12.2 volts for 14 seconds and
stays there. The cycle will repeat if the system voltage again drops below 11.7 volts.
