Normal Operation

WARNING: This page is about a different car, the 2009 Ford Mustang. However, it is still accessible from the selected car via links, so may be relevant.

The heating ventilation air conditioning (HVAC) module includes the heated seat switch buttons and indicators. The heated seat system will function when the HVAC module is ON or OFF. There is a relay box located behind the headlamp switch area containing 2 micro relays for the driver and passenger heated seats. Battery voltage from circuit 1048 (LB/WH) is supplied to the coil and switch of the driver and passenger heated seat relays. When the ignition switch is ON and the engine running, ground is supplied to the driver or passenger heated seat relay coil from the respective heated seat switch in the HVAC to energize the relay. This closes the relay switch and voltage is supplied to the respective seat's cushion and backrest heater mats. The cushion and backrest heater mats are connected in series circuit with ground supplied to the backrest heater mat, completing the heater mat circuit to heat the seat. If the heated seat switch is on when the ignition switch is turned OFF, the heated seat switch will be on when the ignition switch is turned back ON.

This pinpoint test is intended to diagnose the following:

Fuse(s)
Wiring, terminals or connectors
Heated seat switch (part of HVAC module)
Heated seat relay
Cushion heater mat
Backrest heater mat