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2000 Limited Fog Lights Not Working

Post number 9 has been selected as best answered.

Gemelli

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Okay, I have searched and searched and cannot figure this out. I cannot get my fog lights to turn on. Quick backstory. I had the front bumper off for a couple of months. Long story, not pertinent. I put it back on recently and the fog lights worked just fine. I have no clue what happened in the last couple weeks, but they no longer turn on. I have power to the fog lights switch when the parking lights are on, as the switch illuminates. However, when I turn the fog lights on, the green light does not illuminate and the fog lights do not turn on. The bulbs are good. I have tried swapping the switch. I have checked all the fuses that seem to be for the fog lights, although that's a bit confusing. I have swapped the fog light relay. I'm dumbfounded. Help!
 



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Firstly you know the fog lights only work when the headlights are on right?
 






Firstly you know the fog lights only work when the headlights are on right?
The fog lights in my truck come on with just the parking lights, but I did try it with a headlights on as well. I also made sure that the high beams were not on, although I did check it both ways there too.
 






Check the fuses and relays below the air box.
 






I'd double check that I had the right fuse and relay, fuse 8 in the under hood power distribution box and relay under airbox pictured below.

Might help to have a helper, push the fog light button and you're at the relay box to see if you hear a click.

Next I'd use a multimeter to trace where power stops. Pin 3 of the relay should always be live. My wiring diagram shows that the relay coil should only have live input if the low beams are on. Maybe something changed between the model years.

Check for voltage along each point in the circuit and continuity as well. Wiring diagram attached, but as mentioned above, your wiring may be different if you don't need the low beams on to turn fog lights on, but the switch should still trigger the relay coil by grounding it.


Relay Box Under Airbox.jpg
 

Attachments







the limited has the electronic display in the center console, which includes the lamp out module...... maybe this system is smart enough to know the lights were unplugged?
try resetting things by disconnecting the battery

Just spitballing here not sure if it has anything to do with fog light operations or not
 






Okay, now I'm even more confused. Which maybe isn't that hard.

Regarding the passenger compartment fuses, each one has tested good. With the key on, I have no power to fuse numbers

24 clutch starter interrupt anti-theft
28 generic module radio memory seat
33 headlamps DRL instrument cluster

Number 24 never gets power. Number 28 never gets power, although my radio and memory seats work. Number 33 never gets power although, my instrument cluster works. My Explorer is not equipped with DRLs.

Regarding the under hood fuses, number 4 is for the fog lights and DRLs. It has power on both sides. Fuse 8 is for the rear wiper motor, which has power and works properly. I'm sure the confusion there was because of a model year change.

The relay has power at pin 3 at all times. Cycling the fog light switch on and off does not engage the relay. I have tried several relays with no success. Although, I may just go buy a brand new one for fun. I also tested with the headlights on, both high and low beam just in case. Without power getting through the relay, obviously I'm not getting power to either fog light as confirmed with a test light at each pigtail.

Thank you very much for providing the wiring diagram.
 






the limited has the electronic display in the center console, which includes the lamp out module...... maybe this system is smart enough to know the lights were unplugged?
try resetting things by disconnecting the battery

Just spitballing here not sure if it has anything to do with fog light operations or not
That's an interesting thought. I will give that a shot right now while I'm still tinkering with it.
 






The Lamp Out Module is passive, doesn't in itself determine whether any lights going through it come on, so a reset would do nothing... except reset a message on the display perhaps, but not change whether any lights it senses, work or don't. Plus, it does not sense fog lights at all, AFAICT. They don't run through it, while a physical fault on the LOM PCB, could cause other lights that go through it to fail, like headlights, but there is no report of right headlight low beam not working, so we can rule out the LOM.

Nothing you have stated about fuse #s is different between your '00 and the fuse designations I have for my '98. Fuses 24, 28, and 33 are not related, fog lights should still work without those fuses installed at all. I can only assume that when you checked fuse #4, that you checked the correct fuse #4. There are two fuse #4's in the power distribution box, the larger one is for windows, seats, and moon roof. The smaller #4 is for fog lamps and daytime running lamps.

Let's go over what we know for certain. Your dash switch has to have a good ground or else the backlighting that comes on with the other interior lighting would not work. This is the same ground used to ground the relay when triggered.

When the switch is turned on, it should result in very low resistance between pins #3 and #4. If it does not, stays open circuit, then the switch is bad.

If it does create a low resistance connection between #3 and #4, check for low resistance between pin #3's corresponding connector contact, and the fog lamp relay socket contact #2 as shown on the diagram I posted previously. If you don't have low resistance between these two, either a contact or the wire itself between them is faulty.

If you do have low resistance between these two, check resistance between either of those, to chassis ground. Without the relay plugged in, it should have infinite resistance aka open circuit.

Then there is the power wire itself to the fog lamps and the switch-on indicator bulb. You should measure very low (under 5 ohms) resistance between the relay box contact #5, and both the fog lamp socket positive contact, and/or the dash switch contact #6. Check one or the other, no need to check both. If this is bad, I suspect bad contact(s) or a damaged wire, probably near the relay box for it to affect both the dash indicator bulb and the fog lights themselves.

fuses & relays.png
 






Firstly you know the fog lights only work when the headlights are on right?
On my vehicle
The fog light go out when the high beam are on.
The fog lights and low beam are the combination. Both are on
 






I'd double check that I had the right fuse and relay, fuse 8 in the under hood power distribution box and relay under airbox pictured below.

Might help to have a helper, push the fog light button and you're at the relay box to see if you hear a click.

Next I'd use a multimeter to trace where power stops. Pin 3 of the relay should always be live. My wiring diagram shows that the relay coil should only have live input if the low beams are on. Maybe something changed between the model years.

Check for voltage along each point in the circuit and continuity as well. Wiring diagram attached, but as mentioned above, your wiring may be different if you don't need the low beams on to turn fog lights on, but the switch should still trigger the relay coil by grounding it.


View attachment 442675
Thanks for sharing! I must ask, where can I get the complete guide to the wiring system? I've been looking for it for my Explorer XLT 2000 4WD 5.0 V8.

Thanks a lot!
 






Thanks for sharing! I must ask, where can I get the complete guide to the wiring system? I've been looking for it for my Explorer XLT 2000 4WD 5.0 V8.

Thanks a lot!
See the 2nd gen wiring diagrams link in my sig. below.
 












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