Heated Seat Operation

WARNING: This page is about a different car, the 2004 Pontiac Aztek and 2004 Buick Rendezvous. However, it is still accessible from the selected car via links, so may be relevant.

The driver and front passenger seats are heated using electric heater elements with approximately 1 ohm of resistance each and are located in the lower seat cushions and seat backs. Voltage to the heater elements is controlled by the heated seat relay modules using inputs from the heated seat switches and the heated seat thermistors. The heated seat relay modules and thermistors are part of the lower seat cushion heater element assemblies. Ignition voltage is supplied to the heated seat switch assembly and is used to supply a signal voltage to the relay module and to illuminate the heated seat indicator during heated seat operation.

Battery voltage is supplied to the relay module through a PTC device located in the seat harness which provides extra circuit protection. During heated seat operation the relay module switches the battery voltage supply circuit to the heater element supply circuit. The seat cushion and back heater elements are wired in series and always operate simultaneously. The seat temperature is regulated by the relay module using an input from the thermistor located in the seat cushion. The thermistor is a temperature sensitive variable resistor and the relay module determines the seat cushion temperature by monitoring the signal voltage supplied to the thermistor. When the desired seat temperature has been reached the relay module will open and close the supply voltage to the heater elements as necessary in order to maintain the seat temperature.