Astra L4-1.8L (2009)
Seat Heater: Description and Operation
Heated Seats Description and Operation
The heated seat system consists of the following components:
*
Heated seat switch
*
Heated seat control module
*
Seat cushion heater element
*
Seat back heater element
*
Temperature sensor
Heated Seat Switch
The heated seat switch controls the high and low temperature settings through a rocker switch that is located near the HVAC control head. Battery
positive voltage is supplied to the switch from the heated seat fuse located in the fuse block. The heated seat system will operate only with the ignition in
the ON position.
Control Module Power and Ground
Battery positive voltage is supplied at all times to the heated seat module through the battery positive voltage circuit and the HTD SEATS fuse located in
the underhood fuse block. When commanded ON, the heated seat module uses this voltage to heat the seat heating elements. The heated seat module and
the seat heating elements are grounded through the module ground circuit to G301.
Heated Seat Operation
When the heated seat switch is placed in either the high or low temperature position, battery positive voltage is applied through the heated seat switch
signal circuit to the heated seat module. At the same time, battery voltage is also applied through one of two resistors in the switch and the heated seat
HI/LO signal circuit to the module. In response to these switch signals, the heated seat module closes its contacts and applies battery positive voltage
through the heated seat element supply voltage to the seat heating elements. When the heated seat switch is in the HIGH heat position, battery voltage is
applied through a 200 ohm resistor and the module sets the seat temperature to high heat. When the heated seat switch is in the LOW heat position,
battery voltage is applied through a 2,850 ohm resistor and the module sets the seat temperature to low heat.
Temperature Regulation
The heated seat system is designed to warm the seat cushion and seat back to approximately 44°C (111.2°F) when in the high heat mode, or 37°C (98.6°
F) when in the low heat mode. The heated seat module monitors the seat temperature through the temperature sensor signal circuit and the temperature
sensor (thermistor) that is located in the seat cushion. The temperature sensor is a variable resistor, its resistance changes as the temperature of the seat
changes. When the temperature sensor resistance indicates to the heated seat module that the seat cushion has reached the desired temperature, the
module opens its contacts to remove voltage from the heating elements. The heated seat module will then cycle the contacts open and closed to maintain
the desired temperature.
