Seat Temperature Element: Description and Operation

Seat Heaters

How the Circuit Works

With the ignition switch in ON (II), battery voltage is provided through fuse 3 (in the driver's under-dash fuse/relay box) to the coil of the seat heater relay, which is grounded at G201. The coil of the relay is then energized, which closes the relay contacts providing voltage through fuse 3 (in the passenger's under-dash fuse/relay box) 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 passenger's seat heater is located in the seat cushion only.

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 ground G801. Current is limited because it is flowing through both seat heaters in series, making the seat warm enough for moderately cold weather.

When the driver's seat heater 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 seat cushion and seat back heaters. The seat cushion heater is grounded through the WHT/BLU wire and the driver's seat heater switch to G503. The seat back heater is grounded at G801. Since the seat 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 113 ° F (45 ° C) and opens above 140 ° F (60 ° C), while the thermostat is closed below 110 ° F (43 ° C) and opens above 117 ° F (53 ° C). This helps maintain a constant seat temperature and prevent overheating. The front passenger's seat cushion heater works the same way.