Infiniti QX: Windshield deicer (if so equipped) - Rear window and outside mirror defroster/windshield deicer (if so equipped) 
switch - Instruments and controls - Infiniti QX Owner's ManualInfiniti QX: Windshield deicer (if so equipped)

The windshield deicer switch (rear window and outside mirror defroster switch) operates when the ignition switch is in the ON position. The deicer is used to remove ice from the windshield when a wiper is frozen to the windshield. When the switch 1 is pushed, the indicator light 2 illuminates and the deicer operates for approximately 15 minutes. The rear window defroster will activate at the same time. After the preset time has passed, the deicer will turn off automatically. To turn off the deicer manually, push the deicer switch again, and the indicator light turns off.

CAUTION
► When operating the deicer continuously, be sure to start the engine. Otherwise, it may cause the battery to discharge.
► When cleaning the inner side of the window, be careful not to scratch or damage the electrical conductors on the surface of the window.

    Rear window and outside mirror defroster
    To defog/defrost the rear window glass and outside mirrors, start the engine and push the switch 1 on. The indicator light 2 will come on. Push the switch again to turn the defroster off. ...

    See also:

    Additional Program Information
    All program options, such as shuttle service, may not be available at every dealer. Please contact your dealer for specific information about availability. All Courtesy Transportation arrangements w ...

    Freeing a frozen door lock
    To prevent a door lock from freezing, apply deicer through the key hole. If the lock becomes frozen, heat the key before inserting it into the key hole or use the Intelligent Key system. ...

    Emergency key
    Note: There are two designs of Smart Key, refer to the information which is relevant to the design of Smart Key supplied with the vehicle. A. Press emergency key release button and pull out side ...