Seat Temperature Element: Description and Operation

Voltage is supplied through fuse 6 at all times to the seat heater main relay. When you turn the ignition to RUN, voltage is supplied through fuse 8 to the seat heater main relay. The relay is then energized and supplies voltage to the driver's and front passenger's seat heater switches. When you push either seat heater switch to ON, voltage is applied to the respective seat heater relay. Ground is provided for the relay through TH1 to G501 or G502. The relay energizes and its contacts close, providing voltage to the seat back and seat cushion, which are in parallel. The seat cushion heater is grounded directly to G501 or G502, while the seat back heater is grounded through the closed seat heater relay contact to G501 or G502.

Since the seat heaters are in parallel, they quickly heat up to 104°F (40°C) and THi opens, removing ground from the seat heater relay. The seat heater relay deenergizes and its contacts open. Voltage is then applied through the open contact to the seat heaters, which are now in series with each other. The seat heaters now draw less current and therefore producing less heat. When the temperature falls below 104°F (40°C), THi closes and the seat heater relay energizes. THi will open and close to keep the temperature at 104°F (40°C) until you turn the seat heater switch to OFF. BR1 and BR2 are in the circuit to prevent abnormal temperature increases.