DeVille V8-4.6L VIN 9 (1995)
Seat Heater: Description and 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 Driver's and Passenger's Heated
Seat Switches (Deville/Concours), Console Switch (Eldorado/Seville), 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 LO position, voltage from Fuse D5 (Deville/Concours) or A3
(Eldorado/Seville) 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 850 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 Seat 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 Seat 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 seat cushion. The sensor is a variable resistor whose resistance
changes as the temperature of the seat cushion changes. The 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 element 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 850 at ground G302.
