Heated Seats

CIRCUIT OPERATION
The heated seat system is designed to warm the seat cushion and backrest to approximately 37°C (98.6°F) when in the low position and 44°C (111.2°F) when in the HI position. the system will only operate when the ignition is in run. Components in the system are the Console Switch, Driver's and Passenger's Heated Seat Relay Modules and the Heating Elements in the seat cushions.


Operation
When the ignition is in run and the Driver Heated Seat Switch is placed in the low position, voltage from Fuse A3 is applied through the switch contacts to the Driver's Heated Seat Relay Module's on input terminal (terminal C) and the LO/HI input terminal (terminal B).

When voltage is applied to the Driver's Heated Seat Relay Module's on input (terminal C), the module relay contacts close to apply voltage from Fuse D1 to the heating elements in the seat cushions. The heating elements in the seat cushion and backrest are wired in a series circuit and are grounded through CKT 804 to ground G302. The heating elements will now start warming the seat.

Temperature Regulation
The position of the Heated Seat Switch determines the regulated temperature of the seats. If the switch is in the lo position, a 200 ohm resistor is in series with the Heated Seats Relay Module's Lo/Hi input terminal (terminal B). When the switch is in the HI position, a 310 ohm resistor is in series with the Lo/Hi input terminal. the Heated Seats Relay Module differentiates the switch positions by monitoring the voltage drop across the switch.

To regulate the temperature of the seats, a temperature sensor is installed in the rear cushion. The sensor is a variable resistor whose resistance changes as the temperature of the seat changes. The Driver Heated Seat Relay Module monitors the sensor resistance through CKT 952 at the sensor input terminal (terminal E). When the Heated Seat Switch is in the Lo position and the heating elements temperature reaches 37°C (98.6°F), the module opens its contacts to cut "OFF" power to the heating elements.

If the Heated Seat Switch is in the HI position, power will be cut "OFF" when the heating element temperature reaches 44°C (111.2°F). The Heated Seat Relay Module will cycle "ON" and "OFF" to maintain the desired temperature. The cycling will continue until the system is turned "OFF" by either the switch or when the ignition is turned "OFF".

On Indicator
When the Heated Switch is in either the Lo or Hi position, voltage is applied through the closed switch contacts to the ON indicator LED to illuminate the indicator. The indicator is grounded through CKT 804 at ground G302.