Ford Fiesta: Seating / Seats - System Operation and Component Description. Description and Operation

System Operation

Heated Seat Operation

The heated seat system only operates when the engine is running. When the driver or passenger heated seat control switch (located on the instrument panel) is activated, it supplies a momentary ground signal to the BCM . When the BCM receives the heated seat switch signal, it activates the appropriate (driver or passenger) heated seat relay (located in the CJB ). When the heated seat relay is activated, voltage is supplied to the applicable cushion heater mat and backrest heat mat (which is wired in parallel). The cushion heater mats are directly connected to ground to complete the electrical circuit to heat the seat.

Each cushion heater mat contains a non-serviceable internal thermostatic switch that closes when cold to complete the heater grid circuits and heat the seat. When hot, the thermostatic switch opens the heater grid circuits and allows the seat to cool. During normal operation, several minutes may be required before seat temperature is increased and several more minutes of cooling before the heater mats continue with heating. The heated seat indicator illuminates continuously while the thermostatic switch cycles between open and closed.

The seat should be occupied to correctly test for normal operation. Temperature measuring devices do not provide an accurate method for testing heated seat operation as surface temperatures are subject to human and environmental characteristics. Correct testing requires heater mat resistance measurements which have tight tolerances affecting heat cycle time length.

The heated seat system does not time-out. A heated seat remains on until it is turned off by the heated seat switch or the ignition is switched OFF.

Component Description

BCM

The driver and passenger heated seat control switches are hard-wired to the BCM . The BCM controls the operation of the driver and passenger heated seat relays (located in the CJB ). The BCM sends voltage to illuminate the driver or passenger indicator of the heated seat switch(es) to indicate an on state. The BCM remains on until switched off or the ignition is set to OFF. The BCM does not time out.

The BCM is a multifunction module that requires PMI when replaced.
Refer to: Module Configuration - System Operation and Component Description (418-01 Module Configuration, Description and Operation).

Heated Seat Control Switch

The driver and passenger heated seat control switches are momentary contact switches that provide a ground signal to the BCM to activate (or deactivate) the driver or passenger heated seat. Each heated seat control switch contains an indicator which is illuminated by the BCM when the system is active.

Backrest Heater Mat

The backrest heater mat wiring pigtail is connected in parallel to the cushion heater mat. New backrest foam must be installed when installing a new backrest heater mat. The backrest foam should not be reused.

Cushion Heater Mat

Each cushion heater mat contains a non-serviceable internal thermostatic switch that closes when cold to complete the heater grid circuits and heat the seat. When hot, the thermostatic switch opens the heater grid circuits and allows the seat to cool. The backrest heater mat wiring pigtail is connected in parallel to the cushion heater mat. New cushion foam must be installed when installing a new cushion heater mat. The cushion foam should not be reused. If a new cushion heater mat is needed on a front passenger seat, install a new OCS service kit with a heater mat already adhered to the cushion foam pad.