Heated Seats

HEATED SEAT SYSTEM
Individually controlled electrically heated front seats are available factory-installed optional equipment. The seat heaters will only operate when the ignition switch is in the ON position, and the surface temperature at the front seat heating element sensors is below the designed temperature set points of the system. The heated seat system will not operate in ambient temperatures greater than about 32 °C (90 °F).

There are separate three-position switches for each front seat located in the inboard seat cushion side shield. An Off, Low, or High position can be selected with each switch, and Light-Emitting Diodes (LED) for each switch illuminate to give a visual indication that the system is turned on. The Low heat position set point is about 35 °C (90 °F). and the High heat position set point is about 40 °C (100 °F). Each switch controls a Heated Seat Control Module (HSCM) mounted to the seat cushion frame under each front seat.

When a seat heater is turned on, a sensor located near the seat cushion electric heater element provides the HSCM with an input indicating the surface temperature of the seat cushion. If the surface temperature input is below the temperature set point for the selected Low or High switch position, a relay within the HSCM energizes the heating elements in the seat cushion and back. When the sensor input indicates the correct temperature set point has been achieved, the HSCM de-energizes the relay. The HSCM will continue to cycle the relay as needed to maintain the temperature set point.

The HSCM will automatically turn off the heating elements if it detects an open in the sensor circuit, or a short in the heating element circuit causing an excessive current draw. The system is also turned OFF automatically when the ignition switch is turned to the Off position. The control circuit operates on ignition switched battery feed through a fuse in the junction block. The heating elements operate on battery feed supplied through the power seat circuit breaker located in the wire harness under the driver's seat.

Following are general descriptions of the major components in the heated seat system.

HEATED SEAT SWITCH
The heated seat switch is mounted on the inboard seat cushion side shield of each front seat. The two switches, one switch for each front seat, provide a resistor multiplexed signal to their respective Heated Seat Control Module (HSCM). Each switch has an Off, Low, and High position so that both the driver and the front seat passenger can select a preferred seat heating mode.

Each switch has a Light-Emitting Diode (LED), which lights to indicate that the heater for the seat that the switch controls is turned on. The heated seat switches and their LED cannot be repaired. If either switch or LED is faulty, the switch must be replaced.

HEATED SEAT CONTROL MODULE (HSCM)
The Heated Seat Control Module (HSCM) is an electronic thermostatic module designed to operate the electric seat heater elements. Two modules are used in the vehicle, one for each front seat. The HSCM for each seat is installed on front portion of each cushion pan. The wire harness connector is secured by an integral clip to the inside surface of the outboard seat cushion frame.

Inputs to the module include the resistor multiplexed seat switch signal (which includes the seat cushion temperature sensor circuits), an ignition. switched battery feed, a non-switched battery feed, and a ground. The only HSCM output is the feed for the seat heating elements.

The HSCM cannot be repaired and, if faulty or damaged, it must be replaced.

HEATED SEAT ELEMENT AND SENSOR
Two heated seat heating elements are used in each front seat, one for the seat cushion and the other for the seat back. The two elements for each seat are connected in series with the HSCM.

The temperature sensor is a Negative Temperature Coefficient (NTC) thermistor. One temperature sensor is used for each seat, and it is integrated into the seat cushion heating element.

The heating elements are sewn into the seat cushion cover and seat back cover assemblies, which are serviced individually. The heating elements and temperature sensor cannot be repaired and, if faulty or damaged, the affected seat cover assembly must be replaced.