Loose Headlight Mountings
One possibility is that the headlight mountings are loose. This can be caused by wear and tear, or by an impact to the vehicle. If the headlight mountings are loose, the headlights may not be able to stay in place, and they may move up or down when you drive over uneven roads or make sharp turns.
To check the headlight mountings, open the hood of your Miata and look at the headlights from above. There should be two bolts or screws on each side of each headlight. Make sure that these bolts or screws are tight. If they are loose, tighten them until they are snug.
Faulty Headlight Motor
Another possibility is that the headlight motor is faulty. The headlight motor is responsible for moving the headlights up and down. If the headlight motor is faulty, the headlights may not be able to move properly, and they may move up or down randomly.
To check the headlight motor, turn on the headlights and then turn the headlight switch to the "high" position. The headlights should move up and down. If the headlights do not move properly, the headlight motor may be faulty.
Other Problems
In some cases, the headlights moving up or down may be caused by a problem with the headlight switch, the wiring, or the fuse. If you have checked the headlight mountings and the headlight motor and they are both working properly, you should take your Miata to a qualified mechanic to diagnose the problem.
