It sounds like your low beam filament in the headlight bulb is gone. Try replacing the headlight bulb.
Try replacing the plugs and wires
I would first check all fuses. My 2002 uses a weird configuration and requires several fuses to work all of the lights properly.
The 1999 Chevrolet has a separate fuse for the low beam headlights. The low beam headlight fuse, can be found in the fuse box.
Bank 1 would be the drivers side of the engine on your Chevrolet 4.3 liter
Check the bulbs, switch, connectors, relays and possibly fuses, depending on how your vehicle is wired.
How do you remove the dashboard fascia on a 1999 Chevy Astro?
No, but depending on mileage that's probably not the only problem
sounds as if you may need a tune up bad cap and wires will contribute to not starting on rainy and damp days .hope this helps.
have you checked your fuses? it could be as simple as that This is true, there is a separate fuse for the high beams, low beams and radio. Fuses for 1999 LHS are located behind a side panel (drivers side) of the dash next to the steering column. Driver's side door must be open and there is a wiring diagram on this panel.
The cast of Headlights - 1999 includes: Darren Walsh as Angry Kid
Staring at Headlights - 1999 was released on: USA: 4 March 2006
For a 1999 Lincoln Navigator, the headlights typically use a combination of halogen bulbs, specifically the 9007 bulb type for both high and low beams. When replacing headlights, it's essential to ensure they are compatible with the vehicle's electrical system. Consider upgrading to brighter options or LED replacements for better visibility. Always check the owner's manual or consult an auto parts store for the best fit and specifications.