How Do You Diagnose Headlight Problems?

What are the symptoms of a bad headlight switch?

Symptoms of a Bad or Failing Headlight SwitchIssues switching between modes.

One of the most common symptoms of a faulty headlight switch is issues switching between headlight modes.

Issues with the high beams.

None of the lights work..

How do you troubleshoot headlights?

Troubleshoot HeadlightsThe Fix: Replace the burned out bulb.Diagnosis: The problem could be a bad headlight bulb, a loose bulb or corroded bulb socket, a bad ignitor, or a bad ground connection or wiring harness fault at the ignitor. … TIP: Swap the “good” bulb that is working on the other side to the headlamp that is not working.More items…

When I turn my high beams on the lights go out?

Most of the time both bulbs are bad. The connections to the bulbs could be faulty as well. If you’re unable to pinpoint the issue, have a certified technician, like one from YourMechanic, diagnose your lights firsthand for an accurate repair.

What causes headlight to go out?

Bulbs usually don’t burn out together, but it’s still important to rule that out by checking for power. Most total headlight failures are caused by a bad component like a fuse, relay, or module. Wiring problems can also cause both headlights to stop working. … The fix: Replace the bulb, switch, or relay.

How do you check headlight wires?

Unplug the headlight wiring harness from the non-functioning headlight. Connect the negative lead from the voltmeter to the negative battery terminal. Connect the positive lead from the voltmeter to the positive wire on the headlight wiring harness. The positive wire should have power coming through it.

What happens when a headlight relay goes bad?

One of the most common symptoms of a faulty headlight switch is issues switching between headlight modes. If the headlight switch fails or wears out it can cause problems operating the headlights. A broken switch may only work on certain modes, or may cause them to come on and off intermittently and erratically.

What does a bad headlight bulb look like?

One of the first symptoms of a bad or failing headlight bulb is dim headlights. Over time headlight bulbs can wear out and begin to shine noticeably dimmer than when they were new. A dim headlight will not provide proper illumination and is also usually a sign that the bulb is approaching the end of its service life.

Why do my headlights not work but my brights do?

2. Headlight Fuse or Relay is Bad. Like all electrical systems, the headlights in your vehicle have a fuse in the circuit to prevent too much electricity from reaching the bulb. There will also be a headlight relay that switches power from the low beams to the high beams.

How do you fix low beam headlights not working?

4 Steps to Fix a Low Beam Headlight BulbFind the blown out bulb. … Buy the replacement bulb. … Get your tools ready. … Disconnect the negative terminal on the battery. … Remove the trim pieces. … Find the headlight holder. … Disconnect the cables from the headlight. … Remove the headlight bulb from the bulb housing.

Why are my high beams not working?

By far the most common reason your brights will stop working is from a blown fuse or a bad relay. … Or, it could be a bad relay. If the headlight relay has failed, it may not respond when you attempt to switch the high beams on. Replacing the relay should restore the system and get your high beams working once again.

How do you check a headlight relay?

How Can I Test a Headlight Relay?Turn on Your Lights. Turn on your lights. … Listen for the Click. Open the hood, locate the fuse box with the headlight relay or relays, and open it. … Replace the Relay. Have an assistant turn on the headlights. … Multimeter Tests. You can test the relay with a multimeter, but you have to know how to use it.

How do you check a headlight with a multimeter?

Connect the black (negative lead) of the multimeter to a good ground on the frame or to the negative battery terminal. Set the multimeter on the voltage scale for 20 volts. Turn on the headlights and select low beam with the dimmer switch. The reading should be around 12.4 volts or so.

How do you check a headlight switch?

Turn the switch to the parking lights setting and observe the meter. You should see zero or no more than a few Ohms of resistance. Move the negative lead to the output wire for the headlight relay, then turn the switch to the headlights setting and check the meter.

Does one fuse control both headlights?

Solution: If both headlights aren’t working, it’s unlikely that a bulb is at fault. The likely cause is a fuse, headlight relay, headlight switch, dimmer switch or a wiring fault. … Consult your owner’s manual to locate the main fuse for the headlight circuit and replace that fuse with one having the same amp rating.