Principles of Operation
PRINCIPLES OF OPERATIONAuto-Dimming Interior Mirror
The interior rear view mirror may be equipped with an auto-dimming option. This feature automatically reduces the glare caused by headlamps reflecting in the mirror. The auto-dimming feature is disabled when the vehicle is in REVERSE. Power is supplied to the auto-dimming interior mirror when the ignition is in the RUN or ACC position. The auto-dimming interior mirror has 2 photoelectric sensors that detect forward and rear light conditions. Based on these inputs, the automatic dimming feature adjusts the reflectance level of the mirror glass to eliminate unwanted glare. The reflectance level of the mirror glass is variable and depends on the amount of rear glare in relation to ambient light conditions in front of the interior mirror.
When the forward sensor detects daytime conditions, the rear sensor is inactive and the mirror stays in a high reflectance mode. When the forward sensor detects nighttime conditions, the rear sensor is active and detects glare from the headlights of vehicles approaching from the rear or other glare-producing light sources. To provide increased visibility when backing up, the mirror will automatically return to a high reflectance mode whenever the shifter is placed in REVERSE. If the forward or rear sensors are blocked, the automatic dimming interior mirror might not work correctly.
Driver Seat Module
The power driver seat and power exterior mirrors are controlled by the driver seat module (DSM) only when the vehicle is equipped with the programmable/recall memory option.
On the Expedition Limited, the power fold exterior mirror option is controlled by the DSM. Before running a self-test or retrieving codes, the power fold switch must be inactive for at least 30 seconds.
The DSM system consists of the following components:
- DSM
- Driver memory seat switch
- Memory mirror switch
- Memory set switch
- Front vertical seat motor
- Rear vertical seat motor
- Driver horizontal seat motor
- Memory tilt column
- LH memory mirror
- RH memory mirror
- LH power fold motor
- RH power fold motor
The DSM incorporates multiple functions into one module and offers diagnostics to easily locate and repair concerns affecting the subsystems that it controls. If equipped with heated memory mirrors, the heated glass portion of the memory mirror is controlled by the heated back window system and is not monitored by the DSM for electrical concerns.
Power Exterior Mirror Operation Without Memory
The power exterior mirrors are controlled by the power exterior mirror switch and are operational all the time, whether the ignition switch is on or off. Using the power exterior mirror switch, the driver can adjust the driver and passenger exterior mirrors 4 ways.
Up/Down Motion
The power exterior mirrors can be moved up and down under motor control by actuating the power mirrors up/down switch. The power mirror control switch will power the driver or passenger mirror up/down motor until the switch is released or until the travel limit is reached.
Left/Right Motion
The power exterior mirrors can be moved left and right under motor control by actuating the power mirrors left/right switch. The power mirror control switch will power the driver or passenger mirror left/right motor until the switch is released or until the travel limit is reached.
Power Exterior Mirror Operation With Memory
The memory power exterior mirrors feature allows the driver to program personalized mirror positions that can be recalled using the memory switches or remote transmitter. There are 2 memory settings possible. The power driver seat positions are also stored and recalled with the memory exterior mirror positions.
The power exterior mirrors are controlled by the DSM and are operational all the time, whether the ignition switch is on or off. Using the power exterior mirror switch, the driver can adjust the driver and passenger exterior mirrors 4 ways.
Up/Down Motion
The power exterior mirrors can be moved up and down under motor control by actuating the power mirrors up/down switch. The DSM will power the driver or passenger mirror up/down motor until the switch is released or until the travel limit is reached.
Left/Right Motion
The power exterior mirrors can be moved left and right under motor control by actuating the power mirrors left/right switch. The DSM will power the driver or passenger mirror left/right motor until the switch is released or until the travel limit is reached.
Mirror Selection - Driver/Passenger
The driver can select the driver or passenger mirror to be adjusted by setting the mirror select switch to the appropriate position.
Turn Signal Mirror
The exterior mirror may be equipped with a mirror-mounted turn signal assembly. For Diagnosis and Testing or service procedures, refer to Lighting and Horns.
Puddle/Approach Lamps
The exterior mirrors may be equipped with approach or puddle lamps, which will illuminate when the interior lights are turned on by opening a door or by pressing the unlock button on the remote transmitter, if equipped. For diagnosis and testing of the puddle or approach lamps, refer to Lighting and Horns.
Power Folding Exterior Mirrors Power Folding Mirrors
The power folding exterior mirrors are controlled by the driver seat module (DSM). The power folding mirror switch, which is integral to the exterior mirror control switch, sends a signal to the DSM which then supplies power and ground to the exterior mirrors to extend or retract the mirrors.
If the power folding mirrors have been folded or unfolded without using the mirror switch, they must be synchronized. Refer to Exterior Mirror Motor Synchronization - Power Folding.