Seat Heaters

There are 4 seat heater settings available; Off, 1, 2 or 3, which can be set through the TSD. The heat setting is relayed to the vehicle occupants through a graduated display on the TSD.

Operation of the heated seats is controlled by the automatic temperature control (ATC) module. When the automatic temperature control (ATC) module receives a heating request from the TSD, it broadcasts a message to the central junction box (CJB) over the medium speed controller area network (CAN) bus. The central junction box (CJB) then provides a hardwired 12 V supply to the 3 heater elements contained within each seat. The 3 heater elements, 2 in the seat cushion and 1 in the seat squab, are wired in series.

The automatic temperature control (ATC) module monitors seat temperature using a temperature sensor located in each seat cushion. The central junction box (CJB) provides the temperature sensors with a 5 V supply. The level of the returned voltage back to the central junction box (CJB) is proportional to the seat temperature. The value of the return signal is broadcast to the automatic temperature control (ATC) module over the medium speed controller area network (CAN) bus which it then converts into a temperature value to allow it to control seat temperature to the required level.

The automatic temperature control (ATC) module will suspend or disable operation of the seat heaters if any of the following occur:

• Battery voltage exceeds 16.5 ± 0.3 V for more than 5 seconds. Seat heating is re-enabled when battery voltage decreases to 16.2 ± 0.3 V
• If a short or open circuit is detected
• If the seat heat temperature rises significantly above the target temperature setting.

The graduated display on the TSD remains illuminated until the seat heaters are turned off or the engine stops. If the engine is restarted within 30 seconds the seat heater resumes the previous heating level.