1998 Mercury Grand Marquis Owner Guide 1st Printing - Page 43
1998 Mercury Grand Marquis Manual
Page 43 highlights
Controls and features Press the control to turn the mirror on or off. The mirror will automatically return to the normal state whenever the vehicle is placed in R (Reverse) (when the mirror is on) to ensure a bright clear view when backing up. COMP MIRROR ELECTRONIC COMPASS (IF EQUIPPED) The compass reading will remain accurate during most driving conditions. Unknown to the driver, the compass is continuously recalibrating due to magnetic fields and subtle, slow changes in vehicle magnetics which can occur over the life of the vehicle. The compass reading will remain fixed when significant levels are experienced (such as steel bridges). The compass will return to normal operation upon leaving the magnetized area. If highly magnetized items (such as magnetic mount antennas) are placed very near the compass the display will change to "C" for 15 seconds, then display all segments until the magnetized item is removed. Most geographic areas (zones) have a magnetic north compass point that varies slightly from the northerly direction on maps. This variation is four degrees between adjacent zones and will become noticeable as the vehicle crosses multiple zones. A correct zone setting will eliminate this error. Refer to Compass zone adjustment. 43