The HTD SEAT FRONT Fuse 20 supplies battery voltage to the front seat cushion heater modules at all times. The CLAMP Fuse 10 supplies battery voltage to the driver and passenger seat heater switches when the ignition switch is in the ON position. When either seat heater switch is turned on, voltage is applied to the seat cushion heater module through the seat cushion heater control circuit. At the same time, battery voltage is applied to the seat cushion heater module through the seat heater switch signal circuit. With voltage present at both of the module inputs, current flows through the seat cushion heater element and the seat back heater element to ground. The seats heat to a level determined by the position of the seat heater switch. When the switch is moved to a higher position, the voltage applied to the seat cushion heater module through the seat cushion heater control circuit increases. The voltage increase results in an increase in the current flow through the seat cushion heater elements, and the seats become warmer. A sensor in the seat cushion heater monitors and regulates the temperature of the cushion.

When either of the seat heater switches is turned on, voltage is also applied to an LED inside of the switch. The LED illuminates to indicate that the seat cushion heater is on.

The HTD SEAT REAR Fuse 4 supplies battery voltage to the LH and RH rear seat cushion heater relays at all times. When the ignition switch is in the ON position, the CLAMP 15 CRUISE Fuse 15 supplies battery voltage to both of the heater relays.

When the ignition switch is in the ON position and either of the rear seat heater switches is closed, the rear seat cushion heater relay detects battery voltage on the rear seat heater switch signal circuit and the CLAMP 15 CRUISE Fuse 15 circuit. The relay closes, and voltage is applied to the rear seat cushion heater element and rear seat back cushion heater element. The seat cushions heat to a level determined by the heated seat thermal switch. The seat cushion will remain on until the corresponding heater switch is pressed again or the ignition switch is turned to the OFF position.

When the seat cushion relay is energized, battery voltage is also applied to the rear seat heater switch indicator. The indicator illuminates as long as the seat cushion heater is on.

The heated seat thermal switch maintains the heated seat element temperature between 40°C (104°F) and 50°C (122°F). It should be stressed that the thermal switch regulates the temperature of the seat heating element, and not the actual seat cushion temperature. Each seat contains two heating mats and two built-in thermal switches.