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Thread: Fog Light Help

  1. #1

    Default Fog Light Help

    Here is the situation, my 20th Anniversary GT 350 has sat a long time. Here is a thread of my progress in the last month getting this back on the road:

    http://vb.foureyedpride.com/showthre...ersary-Mustang

    Thanks to everyone for their help so far. Onto the Fog Lamps - they don't work. I have all the original Marchal components down to the covers. The hardware such as the porcelain and connectors are in poor shape. Before I restore or replace them I need power to the harness. Sounds simple enough - so here is what I know:

    1. Fuses good
    2. Switch - good, I can also hear the relay click when I turn it on but no amber light to the right when in the on position.
    3. Fog lamps, I believe, get power and ground from passenger side marker light. But have no power.

    My issues start there - marker lights work, but no power to the harness going down to the fog light. Any suggestions? Could the issue be farther in the vehicle such as a relay even though it clicks?

    Once I get power to the harness I will work on the lights but no point until then. Has anyone found a similar replacement fog lamp that looks like the Marchals?

  2. #2

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    Stupid question - Are the headlights on with the fogs? If I remember correctly the fog lights only go on with the headlights.
    Mike
    85 GT - owned since 87

  3. #3
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    Fogs only work with low beams.
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  4. #4

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    Correct I have the low beams on, switch all the way out and there is no power. That’s would have been fantastic if that was it

  5. #5

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    My switch is goofy. The light on it doesnt work, and it only clicks the relay on in one specific position in the center of it's throw. My solution was to unplug the switch and jump the connector with a short length of wire and a couple spade connectors (I like to always have the fog lights on with the lows anyway, so why not).

    I'm simply bringing this up as a troubleshooting step. Doing this is the same as simply eliminating one potential suspect from the list.

    Does the relay have power? If not, does giving it power temporarily from elsewhere cause everything after the relay to start working?

    Just spit balling here
    Triple black '86 GT Convertible 5.0/5spd (T5Z, hurst short throw, VM-1, 93 leather, all black tmi door panels, 93 cobra wing, strut tower brace, sub-frame connectors, 13.5 degrees base timing).

  6. #6

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    I bypassed the switch like you suggested. I hear the relay click when I do that (even though I think my switch is OK - tested with a multi-meter) and am not sure how to test if the relay has power. Do you know how to test that? Side marker lights, low & high beams as well.



    Here is what is odd and maybe it is supposed to work like this. I have continuity at the harness that feeds the fog lights. My thought is a ground but the cables route behind the radiator support and look fine.

    Harness before Fog Lamps:



    Harness that connect the 2 Marchal Fog lamps - I tested this with this wire harness disconnect and had continuity before I plugged in the harness below:



    Next steps? How to I troubleshoot relay, what does it look like and where is it?

    Thanks,

    Mike

  7. #7
    FEP Supporter tbirdman's Avatar
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    I too have issues with the foglights. My problem, I believe, lies with the wiring in the engine compartment between the relay and the starter solenoid. I think I have a damaged fuse link, but am having a difficult time narrowing it down as I am not electrically inclined.

    My question is, can I bypass the factory wiring altogether and run my own wiring, but still use the factory switch below the dash? I don't want to hook up another switch.
    If they take my stapler, then I'll set the building on fire...

    85 Mustang GT

  8. #8

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    If you search the forum post “Fog Lamps” there is a thread on that topic. I read that in detail and the short answer is no you cannot run new wire, you need the resistor in line otherwise you will draw straight 12 volts. The factory fog lamps “tap” into the power of the car using the resistor. There is an article where it explains how to do it - but in essence you are reengineering what is already there. Hence I am trying to find help.

    how to test the resistor?
    how do the fog lights get power?
    what are the layman’s schematics for just the fog lights?

    I am not very technical either, I like it when someone says “the black/red stripe wire should have power when the low beam and fog lamp is on” - ok great let me check that. Or “bypass the switch” ok I understand that, didn’t work.

    its easy to test continuity for broken wires if you know what your looking for. In my case I have continuity all the time and no power/voltage. I am thinking bad cable,grounded, or something along those lines. But I inspected the wiring as far back as it goes and looks great, it was factory wrapped and In a loom.

    i too like you am looking for non super technical answers.

    mike
    Last edited by michaeloberg1980; 01-19-2020 at 06:38 AM.

  9. #9
    FEP Supporter tbirdman's Avatar
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    The relay for the fog lights is this...

    Name:  FL Relay 2.jpg
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    Name:  FL Relay 1.jpg
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    It will be located in front of your left knee (if you were sitting in the driver's seat), under the dash, screwed to the bracing. The screw acts as a ground, so there will not be a ground wire. If you trace back your wire from the fog light switch, it should lead to the relay.

    To the best of my knowledge, the way the system works is as such;

    Power for the fog lights comes in from the engine compartment via a fusible link (splice?) into the relay under the dash. There is wiring that comes from the headlight switch to the multifunction switch, and then runs to the fog light switch. There is then wiring that runs from the fog light switch to the relay. When you turn on the fog light switch, it closes the relay, which in turn sends power out to the fog lights. The headlights have to be on (in low beam) to turn on the fog lights, which is why you have the wiring coming from the headlight/multifunction switch.

    That's the easy part. The hard part (for me) is finding the fusible link in the engine compartment that sends power to the relay. And even if you could find the fusible link, repairing it (if it's damaged, which I think mine is) is a difficult affair. Being able to solder in a new fusible link in a tight space is not easy. And the fusible link is near a group of other fusible links that come out of the main harness that comes from inside the car. Everything is very tight in there. I imagine I could remove the harness to get to the fusible link easier, but that seems a very complicated process.

    The other issue is that the wiring diagrams for my car (an 85) identify the wire color coming in from the fusible link different than the EVTM does. I believe the EVTM is correct, which identifies the wire as orange with black stripes.

    What I guess you need to do is the remove the connector from your relay and see if you are getting power coming in from the fusible link. If you are, and you're getting power coming down from the headlight/multifunction switch, it either has to be the relay of the fog light switch.

    Again, this is all a guess to me, as i'm not an electrical guru. But it makes common sense at least.
    If they take my stapler, then I'll set the building on fire...

    85 Mustang GT

  10. #10
    FEP Supporter tbirdman's Avatar
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    As far as wiring schematics for the fog lamps, I looked in the 1984 wiring diagrams that are at the top of the Electric forum section here, and there is no mention of the fog lights. Not unusual since fog lights weren't available until mid year on the 84's and the date on the wiring diagrams is September 1983. I don't have an 84 EVTM (Electrical, Vacuum Troubleshooting Manual), but you may want to get one, or see if anyone on here has one that they can check for you. Again, the EVTM for 84 may, or may not, have info on the fog lights depending on when the EVTM was published. if you do find and EVTM, keep in mind that there are slight differences in the fog light wiring between 5.0 and the 2.3 turbo cars.
    If they take my stapler, then I'll set the building on fire...

    85 Mustang GT

  11. #11

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    OK I unplugged the harness to the relay, put my voltmeter on it and when I flip the fog lamp switch it reads 11 volts (my battery is a bit low troubleshooting this) and when I shut it off it goes to 0 volts. I would say switch good, and I get power, so would it be the relay? It clicks and can feel it mechanically motion when I touch it and toggle the switch.

    Here is a video, forgive the door buzzer I couldn't hold the button in the whole time and film.

    https://1drv.ms/v/s!ApeQ_ob5LLh50kA7Qvszxfaz6bfd

  12. #12
    FEP Supporter tbirdman's Avatar
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    Here is a scan of the page from my EVTM on the fog lights for a 5.0 car. Your car may be different, but I'm thinking it might be the same...

    Name:  Fog Light Wiring - EVTM.jpg
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    The connector that plugs into the relay should have three wires running to it. On my 85 the wires should be;

    Light Blue with black stripe (wire from the fog light switch)
    Tan with orange stripe (wire going out to fog lights)
    Orange with black stripe (wire coming in from the fusible link, hot at all times)

    See if your wires are the same color.

    Sounds like you have power coming in from the headlight/multifunction switches to the fog light switch, since you have power at the end of the wire that comes from the fog light switch. If you probe the other two wires coming into the connector that plugs into the relay, one should have power to it at all times (the wire coming in from the fusible link), and one won't (the wire going out to the fog lights). If you don't have power at either of the other two wires with the engine running, then my thought would be that you have the same issue I do, a problem with the wire bringing the power to the relay. If you do have power at the orange wire with black stripe, then the problem is probably with the relay.
    Last edited by tbirdman; 01-19-2020 at 01:29 PM.
    If they take my stapler, then I'll set the building on fire...

    85 Mustang GT

  13. #13

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    Amazing - fixed! so I had this fusible link with the shielding worn/burnt off that I had no clue where it went to.



    With your advise on troubleshooting the 3 prongs on the relay harness I found I didn't have constant power. I temporary alligator clipped the rouge wire to the positive side of the solenoid and bam - power to the fogs and the harness!!



    So it think I can help you. There should be a 20 amp fusible link with a heavier gauge (maybe 16 or so) Green/Red stripe that goes into a loom with 4 other wires - heavy gauge yellow, a black, brown, green/pink, green/red.



    All 5 wires go into the passenger side firewall. Check and see if you have those 5 wires and note that the 2 green/red & green/orange wires should be preset. One runs power to the fog lights (used my multi-meter to test continuity to find that) and the other has a fusible link connect to the solenoid.

    Thanks all!!! Now onto the restore of the lights

  14. #14
    FEP Supporter tbirdman's Avatar
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    Congratulations on finding the culprit. What color is your hot wire coming in from the fusible link to the relay?
    If they take my stapler, then I'll set the building on fire...

    85 Mustang GT

  15. #15

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    I will let you know in a few minutes, I am fixing the rouge fusible link the will post!

  16. #16

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    OK in this first picture - back side of harness to relay I have constant power to that Green/Pink ON THE RIGHT (maybe Green/Red) hard to tell - this is the wire I put the fusible 20 amp wire to the hot side of the solenoid. The other wire only BOTTOM LEFT has power with the fog lamp switch on. You need to get that first wire hot from the battery through the loom on passenger side into the firewall.




    Front Side constant power on top, power on bottom left with fog lamp switched on:




    I hope this helps you! Thanks all!!! I am looking for a good pair of Marchal Fog lights if anyone has some or parts. I need to rebuilt mine as they are in rough shape but I have power now!

  17. #17
    FEP Supporter tbirdman's Avatar
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    So here is my dilemma...it seems as though Ford changed things up between the 84.5 and the 85 model years. The coloring of the wires changed, and so did the location of the wires. I'm guessing with the mid year changes Ford made to the GT's, that some of the changes were just additions to what was already existing. Instead of redesigning the harness from the interior into the engine compartment, Ford added on a wiring harness for just the fog lights, which is what looks like you were holding there in the last picture of your third to the last post.

    ]It looks like for 85, they added the fog light wiring into the loom that runs from the passenger compartment into the engine bay. I can't tell where the fog light wiring comes through the firewall at.

    The only thing I can see with some degree of certainty is that the connector that connects into the relay does indeed have the light blue/black striped wire coming into it from the switch, the tan/orange striped wire that runs out to the fog lights (also over to the orange light in the fog light switch to illuminate the switch when the lights are on), and the orange/black striped wire...

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    When I have the headlights on and I check for power at the connector going into the back of the fog light switch, I have power. But I do not have any power coming in from the orange/black striped wire (which I guess would be the same as the green/pink wire in your setup) going into the relay. When I go into the engine bay, The only places I see an orange wire with black stripe is coming out of the loom near the starter relay...

    Name:  20200119_154614_1579467309666_resized copy.jpg
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    I can only see about 1/8" of the wire before it goes into what I'm thinking is the fusible link (the black barrel shaped object). On the other side of the fusible link is a blue wire that has been cut off from whatever it was connected to.

    There is also an orange wire with black stripe running into a gray connector between the firewall and the shock mount...

    Name:  Connector with wire.jpg
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    But it isn't an orange wire with black stripe that is on the other side of the connector. There are three other wires running into that connector with the orange wire, but I have no idea what they, or the connector, is for.

    All these wires disappear into the wire loom, and I can't trace where they go.

    I wish it were as easy as your problem. Maybe it's just me.
    If they take my stapler, then I'll set the building on fire...

    85 Mustang GT

  18. #18

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    So that cut wire - for reasons we don’t know was cut, but If you temporarily connect that to the hot side of the starter solenoid, do you get constant power at the harness for the relay? Sounds dangerous but in all reality that is exactly what I did after you gave me the information regarding the always hot wire. After I did that I just fixed and cleaned up all the wires. I did rip all of the loom and tape from my harness to get to the wires. I used a multi meter and a length of cable to connect at the fog light-then probed the loom wires. You could do the same thing with the “suspect” wire behind your relay to your cut wire. As long as the wire isn’t cut there should be continuity.

  19. #19

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    So that cut wire - for reasons we don’t know was cut, but If you temporarily connect that to the hot side of the starter solenoid, do you get constant power at the harness for the relay? Sounds dangerous but in all reality that is exactly what I did after you gave me the information regarding the always hot wire. After I did that I just fixed and cleaned up all the wires. I did rip all of the loom and tape from my harness to get to the wires. I used a multi meter and a length of cable to connect at the fog light-then probed the loom wires. You could do the same thing with the “suspect” wire behind your relay to your cut wire. As long as the wire isn’t cut there should be continuity.

  20. #20
    FEP Super Member gr79's Avatar
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    I have a Bosch aftermarket fog light kit installed. Similar.
    Lights, relay, Bosch kit harness with fuse, toggle switch. Added indicator light.
    No factory fog harness. Mounted the standard 12v Bosch 5 pin relay near the starter solenoid.
    Instructions said connect one (blue in this case) relay wire to the high beams to allow fogs to work with low but not park or high beams.
    The bulbs also need a good ground to the housings. This is the only issue i had when reinstalling the lights 30 years later.

  21. #21

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    What's funny is I also have an 84 and my wiring and wiring color is different from all of yours for yet another version.

    My fog power was spliced into my yellow defrost power wire at the passenger inner fender. A second tan with red stripe was inside the loom that fed power to the fog lights. A dark brown wire from the passenger marker light to trigger the relay. Also a black wire that was the ground side of the switch light ran to the ground wire also at the passenger side marker light.

    I thought it all out and rewired it myself but I may still have the pieces that I can lay out in a picture but I reused the switch section.
    84 20th Anny 2.3Turbo #1978
    84 Turbo GT 11.70@120MPH 418RWHP
    89 41X Coupe 2200 miles
    96 Mystic Cobra Terminator swap

  22. #22
    FEP Supporter tbirdman's Avatar
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    I tried running power to the wire that is cut in the engine bay, but there is so little wire left on the other side of the black barrel shaped object that it was very difficult and I couldn't get anything. The blue wire on the other side is basically hanging by a couple of strands of metal. I'm guessing that since blue is the color of 20 gauge fusible link and my EVTM indicates the fusible link on the end of the power to relay wire for the fog lights is 20 ga, that the blue wire is the fusible link side of the connection.

    So just spit balling here, I could use this 20 gauge fusible link repair kit from Ford...

    Name:  20ga. Fusible Link.jpg
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    and do one of two things. I can try and dig the orange with black stripe wire out of the loom, cut the black barrel shaped piece (which I assume is the protector that covers the splice) off the end and either crimp or solder the fusible link repair piece on the end of the orange/black stripe wire, then attach the eyelet on the end of the fusible link directly to the starter solenoid hot side.

    Or is that not such a great idea?

    Or, I could get some 16 gauge wire (since from what i understand, a fusible link is designed to protect wire that is 4 sizes larger than the fusible link), again either crimp or solder the repair piece on the end of the 16 ga wire, attach the eyelet to the starter solenoid, run the wire inside the passenger compartment, remove the three point connector from the relay, try and find a matching metal piece that goes inside the connector on the end of the wire, and if I can find that piece, attach that to the end of my 16 ga wire and replace the orange/black stripe wire with my replacement wire. Then I should be able to keep the rest of the factory wiring. I could do this until I can get the loom out of the car to do a better repair.

    How hard is it to get these harnesses out of the car with damaging them or something that they are connected to?
    If they take my stapler, then I'll set the building on fire...

    85 Mustang GT

  23. #23
    FEP Supporter tbirdman's Avatar
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    GT350R, is your car a 5.0, or 2.3 turbo? The fog lights weren't added until the middle of the 84 model year. And prior to them becoming a Ford factory add on, the pieces were available as a dealer installed option. So your fog lights may have been added by the dealer, or michaeloberg1980's may have been added by the dealer. And who knows what they used to wire in the fog lights? Michaeloberg1980's set up sounds closer to my 85 setup except that the wires are different colors and they aren't inside the factory harness coming from the passenger compartment.
    If they take my stapler, then I'll set the building on fire...

    85 Mustang GT

  24. #24

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    Are you trying to restore the wiring or make the fog lights work? That will answer your question on the fusible link.

    In my car (2.3 T), the harness when from the battery on the driver side of the car, across the core support, down the inner fender of the passenger side and through the hole by the heater core. It then went across the dash. the yellow wire went to the rear defrost switch while the fog wiring continued through the dash to the fog light switch.

    I cut everything out. I ran a new fog power wire to a relay I mounted inside my driver side inner fender. It's powered from two wires at my console information center. One from marker lights, and one key on. I did that since the factory relay under the dash is a double power trigger , and self grounding. I grounded the light from the switch at the original relay. I pulled 12 gauge wire from my starter solenoid to my new relay , it's been continues to my fog lights. My fog lights ground through the stud on the fog light bar, with only positive wires running to them.

    So now my original factory relay only operates as a positive trigger to my new relay and thicker power wire.
    Last edited by GT350R; 01-19-2020 at 08:39 PM.
    84 20th Anny 2.3Turbo #1978
    84 Turbo GT 11.70@120MPH 418RWHP
    89 41X Coupe 2200 miles
    96 Mystic Cobra Terminator swap

  25. #25

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    Quote Originally Posted by tbirdman View Post
    GT350R, is your car a 5.0, or 2.3 turbo? The fog lights weren't added until the middle of the 84 model year. And prior to them becoming a Ford factory add on, the pieces were available as a dealer installed option. So your fog lights may have been added by the dealer, or michaeloberg1980's may have been added by the dealer.
    20th Anny GT350 like his. Mine is 2.3t though.
    84 20th Anny 2.3Turbo #1978
    84 Turbo GT 11.70@120MPH 418RWHP
    89 41X Coupe 2200 miles
    96 Mystic Cobra Terminator swap

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