1998 Lincoln Navigator Owner's Manual - Page 167

Maintenance and care AIMING THE HEADLAMPS Your vehicle is equipped with a Vehicle Headlamp Aim Device (VHAD) on each headlamp. Each headlamp may be properly aimed in the vertical (up/down) and the horizontal (left/right) directions using your VHAD system. The headlamps on your vehicle are properly aimed at the assembly plant, and vertical and horizontal indicators of the VHAD system are calibrated. A bubble (vertical indicator) that is not centered between the two red lines does not necessarily indicate out-of-aim headlamps. If your vehicle is not positioned on a level surface, the slope will be included in the vertical indication. Therefore, vertical and horizontal headlamp adjustment should be performed only when the beam direction appears to be incorrect. You will need one 4 mm wrench or socket with ratchet to make the adjustments. The following procedure assumes that the factory set horizontal indicator reference has not changed and the vehicle's front structure is in its factory alignment condition. If the vehicle has been in an accident requiring the front end of the vehicle to be repaired, the horizontal indicator should be recalibrated by the servicing facility according to instructions in the vehicle's Workshop Manual. D U 167