F150 Low Beam Headlights Not Working - Diagnosis Advice

F150 Lowbeam Headlights

A low beam headlight isn't very glamorous, but it's a pretty vital piece of safety equipment. When the low beams stop working (or work intermittently), your only options are to either a) drive with your high beams on (something that might incite a case of road rage) or b) drive without lights at all. 

Of course, option "C" is to get them working again. Here are some tips for getting them operational:

Issue: My low beams are not working, but my high beams are working.

What to do:

  • If your low beams are not working, but your high beams are, there is a possibility that your low beams have burned out in your headlight. They get the most use, so they are the first to go. Replace the headlamps.

Issue: My low beams work intermittently.

What to do:

  • If one headlight works intermittently, the bulb may be on its way to being burned out. Replace the bad bulb.
    If both lights are doing the same thing, then the problem may lie in the wiring or the fuses. Make sure that all your fuses are set correctly and not loose. A headlight should not be loose, so make sure they are both sitting solidly in the sockets. Intermittent connection is generally an electrical issue, so trace the wires back to ensure that they are all solidly connected. You may have a wire that is not completely connected and is being moved around as the car moves.

Issue: One of my low beams is working and the other is not.

What to do:

  • If one is working and the other one is not, then swap your headlights to see if there is an issue with the lamp or the electrical connection to the lamp. A lamp that works on one side and not the other is an indication that the bulb is fine and the issue is elsewhere. Check the electrical connection to the lamp for a loose wire or wires that have been damaged. You can test the socket with a voltmeter with the engine on. If there is no voltage, the wiring or switch has gone bad.

Issue: My low beams are not working at all.

What to do:

    • If both of your headlights are no longer working, then it may be a fuse. Check your fuses to ensure that the fuse is good, and replace it if you can see that it is burned out. If the fuse is good, then it may be an electrical issue that goes from the fuse to the lamps. You may need a mechanic to trace the electrical wiring to be sure.

Usually diagnosing and correcting a low beam issue is relatively simple. It is a lamp that is going bad, a loose connection or a blown fuse. Other issue with the electrical system may cause the headlights to behave erratically, so if you rule out these issues, then you may wish to contact your local mechanic for a thorough diagnosis of the electrical system.