Seat Temperature Element: Description and Operation

How The Circuit Works

With the ignition switch in ON (II), battery voltage is provided through fuse 4 (in the driver's under-dash fuse/relay box) to the coil of the seat heater relay which is grounded at G301. The coil of the relay is then energized, which closes the relay contacts providing voltage through fuse 62 (in the multi-fuse/relay box B) and the relay to both seat heater switches.

Two heaters are provided in the driver's seat. One is located in the seat cushion and the other is in the seat back. The front passenger's seat has only one healer in the seat cushion.

When the driver's seat heater switch is in the LOW position, current flows in series through the seat heater switch, the WHT/BLU wire, and the seat cushion and seat back heaters to G551. Current is limited because it is flowing through both seat healers in series, making the seat warm enough to be comfortable in moderately cold weather.

When the switch is in the HIGH position, current flows in parallel through the seat heater switch, the WHT/RED wire, the circuit breaker and thermostat, and through the cushion and seat back heaters. The cushion heater is grounded through the WHT/BLU wire and the driver's seat heater switch to G401. The seat back heater is grounded at G551. Since the cushion and seat back heaters are now in parallel, current flow through them increases and the seat warms to its maximum temperature.

The circuit breaker is closed below 86°F (30°C) and opens above 122 °F (50 °C), while the thermostat is closed below 93°F (34 °C) and opens above 109°F (43 °C). This helps maintain a constant seat temperature and prevent overheating. The front passenger's seat heater work the same way.