by going to a body shop
replace it
There should be six signal lights on the mystique, two front, to rear, and two sidemarker lights.
below the fog lights there is one on each side
yes there are why dont your look it up yourself
replace battery or alternator
You have to start by checking the bulbs or the flasher I think it may be the flasher.>>>>>>>>>>>>>
On a 1999 Mercury Mystique, the light control for the door lights is typically located on the driver's side door panel. You'll find a switch that controls the interior lights, including the lights that illuminate when the doors are opened. If the lights are not functioning, check the door switch, which may be stuck or malfunctioning. Additionally, ensure that the vehicle's interior light settings are adjusted correctly.
Replace the bulb first, if this does not work try the reverse switch.
check your owner's manual
yep, that just might be the case, i just actually walked in from fixing the same problem, just replace the fuse and it should be fine
check fuses & brake lights switch located on brake pedal
Sixth fuse slot in the upper row of the under dash fuse box. 15A (blue)