The troubleshooting process you follow will depend on the pop in of failure that youre dealing with.
High intensity discharge (HID) headlights can also fail due to other associated components.
Neither of the headlights work.
Bulbs usually dont burn out together, but its still important to rule that out by checking for power.
Most total headlight failures are triggered by a bad component like a fuse, relay, or module.
Wiring problems can also cause both headlights to stop working.
High beam headlights dont work or low beams dont work.
Headlights work but seem dim.
The cause: Foggy lenses, worn out bulbs, or a charging system issue.
The fix: Clean the lenses, replace the bulbs, or repair the charging system.
If your headlights always seem dim, the problem could be foggy lenses or worn out bulbs.
If your headlights seem to dim during specific circumstances, there may be a charging system issue.
How Do Headlights Work?
When you turn on your headlights, that switch activates a relay.
That relay, in turn, actually provides the electrical connection between your headlight bulbs and the battery.
Fuses are also involved to make it provide a sacrificial failure point to protect the rest of the wiring.
In the case of dual filament headlight capsules, this literally sends power to the high beam filament.
If any of these components stop working properly, your headlights will fail.
Fix It Yourself or Take It to a Mechanic?
The diagnostic procedure that a professional technician will actually follow is similar to the one outlined below.
So its actually pretty common to have one bulb burn out before the other.
If the connector has come loose, pushing it back on may fix the problem.
Regularhalogen capsules can last anywhere from 500 to 1,000 hours.
So if yours didnt last that long, there may be another issue at work.
One easy thing to look for is any water or condensation inside the headlight assembly.
If this is the case, then replacing the bulbs should fix your problem.
If you find a blown fuse, then replacing it may fix the problem.
When replacing a blown headlight fuse, its important to use a new one with the same amperage rating.
You should find battery voltage on both sides of the fuse.
If you dont, then youll need to look at the wiring between the fuse block and the battery.
The next step is to locate and inspect the headlight relay.
Discoloration on the base or terminals may also indicate a problem.
In that case, it’s possible for you to easily swap the headlight relay with an identical component.
If the headlights start working at that point, then the relay was the problem.
Beyond that, the diagnostic procedure is a little more complicated.
In those cases, the best course of action is to rule out everything another component first.
The same is true if one bulb works on high beams but now low.
What Causes Headlights to Seem Dim?
When headlights stop working, they generally stop working altogether.
The first is that headlights actually do lose brightness as they age.
Dirty, foggy, or oxidized headlight lenses can also cause an issue by blocking some of the light.
In some cases, you will have to actually replace the headlight assembly.
Often it’s possible for you to fix oxidation of headlight lens covers withheadlight reconditioning.
This is a process that involves removing the oxidation with an abrasive and then applying a protective clear coat.
The most common culprit is a bad alternator or a loose belt.
You may destroy, or drastically shorten the life of, your good bulb.
The problem could also be related to a fuse, or a damaged filament.
There are a couple possibilities, but it’s most likely electrical.
