The problem started after a heavy rain. The driver side has both low and high beam but the passenger low beam didn't work. Changed the suspect bulb and no change. Metered the headlight assembly and had 12V on the high beam side and about 10V on the low beam side. Looked for corrosion in the socket and the connection to the wire harness. Installed a new socket with the same result. This morning had both low beams but no passenger high beam. I thought about removing and cleaning the auto lamp headlight switch but since this problem isn't common to both sides, I doubt that will fix the problem. Suspecting a weird wire harness issue. Anyone encounter this problem? Changed the multifunction switch a couple of years ago due to a failing turn signal. I have and electronics/electrical background.
Hi Steven, I guess you have checked the fuses? Some time (and I'n not saying this is your problem) the fuses are wired in such a way that if one blows (and the fuse is on the earth side of the circuit) there will be an output, but the circuit will either use the earth through the the other bulb or fail to earth. I would also suggest having a look at the relays and their operation. Lastly, check the earth connections again. Regards John
SOURCE: The driver side headlight works
You replace the bulb
You do however have to remove to entire
light housing assy
Should be 2 screws on top and one not so
fun to reach down in the back
SOURCE: I have a 2004 Lincoln Navigator. The passenger
I would check the assembly itself. Where the pigtail plugs in, make sure that the elements are not burnt or corroded.
SOURCE: replace passenger side low beam bulb in a 2003 lincoln aviator
Open hood and remove the radiator site shield and the air delector on top of the headlamp assembly. You will then see 2 clips that you will pull up and then remove the headlamp assembly.
SOURCE: 97 linc town car/ at night the auto head lights
I think the head light circut breaker is at fault. I need a wiring circut diagram
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Hi John, no I didn't check fuses or relays yet. I didn't suspect them initially as I was able to get some to full voltage at the connections, but I will today. With reduced voltage, I suspected that something such as corrosion was potentially creating a resistance. Didn't check the grounds - again for the same voltage reason - unless each light has it's own grounding circuit, I would've expected a common problem with each headlight side.
Thanks for your ideas. I'll let you know what I find out.
No issue on how to remove the headlight assembly. The OEM's were replaced 2 years ago.
Did a continuity check on the headlight assembly wiring and it passed with 0 ohms. Examined the wiring and moved the wiring around looking for internal wiring corrosion or a intermittent break. 0 ohms of resistance so I'm confident in this portion of the circuit.
Just checked them again this morning and both low and high beams are functioning.
Thinking back, my father-in-law mentioned he'd had trouble with a leak around the windshield which allowed water to gather on the passenger side floorboard, soaking the carpet. Sometimes he'd notice the water on the inside of the windshield. The point for my question is this...is there some lighting control module or electrical connection on the passenger side that could affect headlight operation? We do not get the number of rain storms or severity of the them as he encounters near the Gulf coast so if this is a rain related failure, it'll be somewhat difficult to diagnose.
Will still check relays and fuses, but with 30 years of experience, I've not seen a fuse that blows partially. They meter either 0 or infinite ohms. Relays could produce some resistance over time on the contacts due to arcing but I looked over a chassis schematic and do not find a reference to a relay associated with the headlight circuit.
Checked the fuses and relays all metered fine and operational.
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