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Discussion Starter · #1 ·
Hello, Yesterday we noticed the right side head light was not working. Neither high or low beam are working. Here's what I checked:
No power getting to the plug at the back of the headlight bulb.
All Fuses are intact (Fuse #29 is for the Right Side Head lights).
Changed Bulb just because.

How should I proceed? Is there a Relay I'm not finding? I have the owners manual and the Shop Manuals. Neither go into too much detail about what might be wrong. Tomorrow I'll start tracing the Wiring Diagram I guess...

TIA,
LarryT
2006 Explorer 4.0L 4WD
Va.
 

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Obviously there is far more to the headlights than just the battery running through the dash switch, and there is a relay, but both headlights share the same circuit until it branches off between the two so with the left working it would have to be something after the circuit split.

I don't have an '06 wiring diagram but looking at one for an older generation suggests the following:

- After the MFS (multi-function switch, on the steering column to select hi/low beams, flash to pass, etc) is where it splits and there should be two separate fuses in the interior fuse panel for L & R headlights.

- Next if you have a LOM (Lamp Out Module) that tells you a light is out, it is possible that has a fault, commonly they pass the lamp current through a power resistor in series (to measure voltage drop) and those resistors can get hot enough to break the solder joints or lift the copper off the circuit board in the long term. I can't tell you for certain where your LOM is located (if you even have one) but on earlier generations of Explorer it was under the floor center console. If you have one (might be an accessory package not found on all vehicles) and it's the fault, and you have even modest soldering skills, they are not too hard to repair by redoing the solder joints or adding a piece of wire if the PCB copper is compromised.

- After the LOM it goes straight to the headlights, two separate wires. If the LOM has become more sophisticated, this could affect both high and low beams, but in the past the LOM only indicated low beams out and high were still on a shared circuit path.

- Depending on the above issue, I would ignore high beams for the moment and focus on the low. You should be able to use a multimeter to measure resistance or continuity between the respective fuse in the interior panel for each side, and the positive bulb connector contact for low beam. If it is open circuit instead of low resistance you have a break in the circuit between these two points.

- Similarly you should be able to measure 12V at the fuse for each side when the lights should be on. Since the left side works, you can compare the left fuse to the right fuse for this 12V reading.

- Inspect the bulb connector for signs of corrosion. Often (not 100% sure on an '06) there is a different colored plastic tab on the connector which if removed, allows pulling the wire socket pins out for better examination if you cannot see them in the plug with a strong flashlight.

- If you had not already found no 12V getting to the socket, next I would have suggested using a multimeter to measure continuity (better resistance) between the bulb negative and chassis ground.

If you do find a blown fuse it is possible you also have a wiring fault, that it has frayed (or rodent chewed it or whatever) and it is intermittently shorting out.

As far as the shop manual providing steps to take, you just do as above or find a known correct wiring diagram for an '06 and using a multimeter set to voltage you can follow the circuit checking for 12V at every point along it.

I'll attach the circuit diagram I was looking at for a 2nd gen Explorer below. Also below is a link in case it is too high resolution to appear inline in this post.
https://i.imgur.com/6DeWJVJ.png

 

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Discussion Starter · #3 ·
ok, thanks much for the well thought out reply. I performed another test this afternoon using a basic Test Light as I think my DMM was not working properly. BTW, I have wiring diagrams for my 06 but the Test light shows this: Holding the connector with the catch at the bottom I tested each of the 3 pins that attach to the bulb. Pin 1 at far left lights with Low Beams on. Pin 3 Lights with High beams on and the pin in the middle tests as a Ground wire. After much searching thru the WD I found connector for the R Headlight.
Pin # Circuit Gauge Function
1 CLF05 (BU-GN) 18 CTRL MOD BEAM, LOW RIGHT
2 GD123 (BK-GY) 18 GROUND - FENDER FRONT LEFT
3 CLF03 (VT-OG) 18 CTRL MOD - BEAM, HI

This seems to confirm my Test Light findings. Now I am really wondering what's going on. BTW, before all this happened I installed LED bulbs - complete replacement H13 bulbs with no other components needed. I had trouble adjusting the new bulbs and put the old ones back in. Immed. we found the Right HI and Low no longer worked.
Thanks for the WD you used! I'll go back and search for the LOW more. We do seem to have one as there's a screen in the Dash with warnings when bulbs don't work or doors are ajar, etc. I saw the video showing the LOM under the dash. Not looking forward to that job!
Comments?
LarryT
 

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Discussion Starter · #4 ·
Well, this is strange! After dinner I pulled the R Head light assy (Again! I'm getting really good at it now) and tried one of the LED Bulbs I had used last week. To my surprise, my headlights now work as they should! Sheesh. This has been frustrating. But I'm glad it's working. Maybe the new one I bought was DOA? I hear a lot about modern electronics being dead out of the box.\
Thanks for everyone's help!
 

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It is odd if your test light indicates power getting to the bulb socket but the bulb doesn't light, unless the LED bulbs had out of spec connector pins that have bent the factory harness connector contacts out of shape.

However I suppose it is possible you have a frayed wire somewhere that's barely passing any current, enough to get the test light to work? If you have some spare pieces of wire lying around of suitably small size, you might try wrapping wire around the contacts and the connector socket to see if that works and if you get your multimeter working if you can measure any current flow or voltage that way.

Unless your LED bulb installation included using a ballast resistor (putting extra load on the circuit), LED bulbs alone should have drawn less current, but if you did or they already had a load resistor built in to fool light out modules, it is possible it was an excessive load that did overheat the LOM and cause a problem.

I'm not familiar with how to pull the center console panel on an '06. On my '98 the middle/top panel comes off while the sides can stay attached to the floor to gain access to the LOM... except mine doesn't have the LOM, I'm just going by memory of what others have had to do to access it.

Anyway if you think it is the LOM and can get it out, it shouldn't be hard to open and inspect the circuit board. Here are some pictures of one in an earlier generation Explorer, which may or may not be the same LOM in yours. For that matter it may not even be a separate module, could have been integrated into the body computer at some point.

http://www.esysdev.com/FordExplorerLOM/
 

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Discussion Starter · #6 ·
Thanks for the response! I put the original bulbs back in (again) and surprise! Both work and can be adjusted... For some reason the LEDs did not respond to movement of the adjusting screw - still scratching my bald head over that as the OEM bulbs adjusted just fine.
Anyway, for now at least, the headlights work as they should (the wife is happy) so I will keep an eye on it and leave them alone as long as they work...

Thanks again!
LarryT
 

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Discussion Starter · #7 ·
BTW, are there any lighting components that might take themselves out of service if they see an unusual level of power being drawn by the lights which would "reset" itself if things return to normal?
 

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No, as far as I know (including looking at the wiring diagram) there are no resettable fuses or breakers nor anything else like that in the vehicle, just regular fuses that blow if current is too high and then must be replaced. However I don't have your generation of vehicle, but have never heard of anything like this after years on a couple different Explorer forums. Manufacturers tend not to use resettable fuses because resetting them before the fault is fixed can be a fire hazard, and they are bulkier and more expensive, and less reliable long term than a simple fuse.

My two best guesses are that either the LED light contacts bent the factory harness connector contacts and they don't make as good a contact as they used to, or you have a bad spot on the wire going to it and it is occasionally shorting out against the (grounded) body or engine somewhere, though I would have thought that might blow the fuse if bad enough to completely keep the light from coming on.
 
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