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  1. #1

    Default A few light issues on my 1986 GT...

    Hello everyone! This past September I was able to purchase a 1986 GT. As result of ownership of this car, I am very excited to be apart of this awesome forum that I have been following for a while before I got the car.

    The car has 168,000 km and the motor and transmission is original to the car. I did not buy it from the original owner BUT I was able to contact the original owner on Facebook (yay technology)!

    They were able to inform me about some neat information on the car such as it was purchased from Ed Learn Ford in St. Catharines, Niagara, Ontario in October 1986 where the original owner owned it until 1991 or so. They were meticulous about the car which is why I think it has remained in good aesthetic condition for all these years inside and out! They informed me that in ‘87 the original 10 hole rims were stolen along with the Marchal Foglights (one of my lighting issues). They perps were caught sometime after the insurance company replaced the factory 10 holes. The foglights were not replaced with marchal’s but some other OEM fog light.

    So, onto the issues!

    Firstly: the foglights, if I pull on the light switch to activate the headlights and then switch the fog light switch I hear a relay clicking but I don’t get and fog light illumination. I have also tried with the ignition turned over and still same result, no illumination..

    Secondly: the headlights, if I pull on the light switch the LP beam lights come on with no issue. However when I pull the hi beam switch on the steering wheel column the flash to pass flashes the Lo beam and the high beams don’t actually stay lit or come on... again car is on or off..

    Thirdly: my swivel map light doesn’t work, I put in a fresh bulb too.. gotta take it off and see underneath..

    Fourthly: my footwell interior lights do not come on, I haven’t checked the bulbs yet down there and will do that but is this normal?!


    Thank you to anyone and everyone who answers here! I appreciate some direction with this, even a small bit of information as I become more familiar with the car. I will post updates as well as time goes on. As you can see in the photo below, my interior is in need of getting those foot well lights fixed!

    Thanks!
    Marco








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  2. #2
    FEP Senior Member liv2roc's Avatar
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    about number four, with key in ignition but not on open drivers door does it buzz. if not the door switch is bad or its a fuse. after looking at the wiring diagram I would say its a possible bad headlight switch. all those light are powered thought it.
    Last edited by liv2roc; 11-11-2019 at 08:56 PM.

  3. #3
    FEP Senior Member Tigger's Avatar
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    About the map light.... the terminals could be corroded. I’ve taken apart quite a few map lights and retinned the terminals with solder. Once I do that they work. There is a how to article posted somewhere that gives detailed instructions. I will look tomorrow and see if I can fine it. If I find it I will post the link.
    67 Mustang Coupe
    96 Tangerine GT
    86 Saleen #179

  4. #4
    Moderator wraithracing's Avatar
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    First as mentioned above a new headlight switch for fog light equipped cars would be my first choice. See what effect that has on your first two lighting issues.

    The high beam issues may be a bad multi-function switch on the steering column. Due to age and use that is not an uncommon issue either.

    As stated above, check your door switches on both doors. A pair of new switches with boots is not a cheap repair, but that can fix your interior light issues. Does the dome light come on with a door open? If none of the interior lights come on, then definitely check the door switches in the front door jamb by the lower hinge. If the dome light works, but not the footwell lights, then their may be a wiring issue or some thing disconnected.

    The map light assembly was prone to issues due to being a heavy metal swivel light and the plastic housing. Not uncommon for the solder connections inside to break due to that. Corrosion can also prevent a good contact. Luckily if yours is bad, Daniel Carpenter just released a reproduction so that helps a lot. https://lmr.com/item/LRS-13776/musta...assembly-85-90

    Good Luck!
    ​Trey

    "I Don't build it hoping for your approval! I built it because it meets mine!"

    "I've spent most of my money on Mustangs, racing, and women... the rest I just wasted."

    Mustangs Past: Too many to remember!
    Current Mustangs:
    1969 Mach 1
    1979 Pace Car now 5.0/5 speed
    1982 GT Stalled RestoModification
    1984 SVO Still Waiting Restoration
    1986 GT Under going Wide Body Conversion Currently

    Current Capris:
    1981 Capri Roller
    1981 Capri Black Magic Roller Basket Case
    1982 Capri RS 5.0/4spd T-top Full Restoration Stalled in TX
    1984 Capri RS T-top Roller
    1983-84 Gloy Racing Trans Am/IMSA Body Parts

  5. #5

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    Quote Originally Posted by liv2roc View Post
    about number four, with key in ignition but not on open drivers door does it buzz. if not the door switch is bad or its a fuse. after looking at the wiring diagram I would say its a possible bad headlight switch. all those light are powered thought it.
    Thank you for the reply!

    When the key is in the ignition I get a door chime with the door open (I believe mine was a late 86 build that adopted a chime box - I prefer the buzzer box!) but I will admit that the chime is intermittent... sometimes it’s there and sometimes it’s not. I am led to believe it could be the actual headlight switch as well. Will need to buy a new one to replace it!


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  6. #6

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    Quote Originally Posted by Tigger View Post
    About the map light.... the terminals could be corroded. I’ve taken apart quite a few map lights and retinned the terminals with solder. Once I do that they work. There is a how to article posted somewhere that gives detailed instructions. I will look tomorrow and see if I can fine it. If I find it I will post the link.
    Thanks for the reply!
    I will take it apart and post a picture of it on here and maybe you can chime in further to see if there are some bad spots that need to be cleaned? Appreciate you looking for the article!!!

    Thanks!


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  7. #7

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    Quote Originally Posted by wraithracing View Post
    First as mentioned above a new headlight switch for fog light equipped cars would be my first choice. See what effect that has on your first two lighting issues.

    The high beam issues may be a bad multi-function switch on the steering column. Due to age and use that is not an uncommon issue either.

    As stated above, check your door switches on both doors. A pair of new switches with boots is not a cheap repair, but that can fix your interior light issues. Does the dome light come on with a door open? If none of the interior lights come on, then definitely check the door switches in the front door jamb by the lower hinge. If the dome light works, but not the footwell lights, then their may be a wiring issue or some thing disconnected.

    The map light assembly was prone to issues due to being a heavy metal swivel light and the plastic housing. Not uncommon for the solder connections inside to break due to that. Corrosion can also prevent a good contact. Luckily if yours is bad, Daniel Carpenter just released a reproduction so that helps a lot. https://lmr.com/item/LRS-13776/musta...assembly-85-90

    Good Luck!
    Do you (or anyone else visiting) happen to have a part number for the headlight switch? I know Dorman makes one but can’t seem to find the right part number...

    Could the actual hi beam bulbs be a culprit as well ? I am wonder how else to determine if the hi beam multi switch is bad..

    The dome light does come on! I didn’t think of that, so it’s either the bulbs are burnt or something in the wiring is disconnected.

    Thanks for the link I will check out that new replacement and as the poster above you mentioned I will post a photo so that way more experienced eyes can see if there is a connection issue with the map light

    Thank you for all the input guys! I really appreciate the wealth of knowledge the forum has to offer a noob like me.

    Marco



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  8. #8
    Moderator wraithracing's Avatar
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    I believe the correct Standard Ignition/Standard Motor Products is DS218. You should be able to pick that up a Oreilly Auto Parts or you can order it online from Rock Auto. I always recommend comparing the new part to your existing light switch to be sure.

    In regards to the high beams do any of the 4 light high beams come on? one the outer two lights are on for low beams and all 4 headlights are on for high beams. If only your low beams come on, then the odds are its the switch in the column as it's doubtful that all 4 high beam elements are bad. You can always pull a plug off and check with a test light for voltage with the high beams on just to be sure. If the high beam indicator in the instrument cluster isn't illuminated, then again its probably the column switch.
    ​Trey

    "I Don't build it hoping for your approval! I built it because it meets mine!"

    "I've spent most of my money on Mustangs, racing, and women... the rest I just wasted."

    Mustangs Past: Too many to remember!
    Current Mustangs:
    1969 Mach 1
    1979 Pace Car now 5.0/5 speed
    1982 GT Stalled RestoModification
    1984 SVO Still Waiting Restoration
    1986 GT Under going Wide Body Conversion Currently

    Current Capris:
    1981 Capri Roller
    1981 Capri Black Magic Roller Basket Case
    1982 Capri RS 5.0/4spd T-top Full Restoration Stalled in TX
    1984 Capri RS T-top Roller
    1983-84 Gloy Racing Trans Am/IMSA Body Parts

  9. #9

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    Quote Originally Posted by wraithracing View Post
    I believe the correct Standard Ignition/Standard Motor Products is DS218. You should be able to pick that up a Oreilly Auto Parts or you can order it online from Rock Auto. I always recommend comparing the new part to your existing light switch to be sure.

    In regards to the high beams do any of the 4 light high beams come on? one the outer two lights are on for low beams and all 4 headlights are on for high beams. If only your low beams come on, then the odds are its the switch in the column as it's doubtful that all 4 high beam elements are bad. You can always pull a plug off and check with a test light for voltage with the high beams on just to be sure. If the high beam indicator in the instrument cluster isn't illuminated, then again its probably the column switch.

    Thanks for the response! I did also confirm with my local auto parts supplier it is DS-218 w/visibility group (meaning fog lights I guess?)
    In regard to the high beam, none of the hi beams come on when I activate the switch, the lo beams only illuminate and appear brighter so they are switching to a hi beam mode? I am wondering if the correct bulbs are even installed in those lo beams now...? I figured that when the hi beams are activated the 2 lo beams stay the way they are and simply are joined by 2 hi beams illuminating? The hi beam indicator does come on (blue light on the tach), do you still think it's the switch or could it simply be bulb/wiring of the lights? You're a great help so far! Thanks!!!

  10. #10
    Moderator wraithracing's Avatar
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    The outside headlights are dual element bulbs. There are three electrical leads on the outer lights. One is ground, one is low beam, and the other is high beam. The inner lights are high beam single element only, therefore they only illuminate when the high beams are on. There are two electrical leads on the inner lights, one for ground and the other for high beam. The Low beam will have the low beam element illuminate on low beam and then switch to the high beam element when you switch for the high beams.

    Sounds to be like the inner lights may be bad, not connected, or something else. I would remove one or both and check to see first if they are connected. Next I would check for power at the pigtail when the high beams are on. If you have power at the pigtail(s), but no actual illumination then most likely the bulbs are bad and should be replaced. If you don't have power at the pigtail, then you will need to check the wiring and figure out why you have no power. The wiring pretty much loops from the low beams to the high beams, so should be an easy check to verify if something is wrong with the wiring. Hope that helps! Good Luck!
    ​Trey

    "I Don't build it hoping for your approval! I built it because it meets mine!"

    "I've spent most of my money on Mustangs, racing, and women... the rest I just wasted."

    Mustangs Past: Too many to remember!
    Current Mustangs:
    1969 Mach 1
    1979 Pace Car now 5.0/5 speed
    1982 GT Stalled RestoModification
    1984 SVO Still Waiting Restoration
    1986 GT Under going Wide Body Conversion Currently

    Current Capris:
    1981 Capri Roller
    1981 Capri Black Magic Roller Basket Case
    1982 Capri RS 5.0/4spd T-top Full Restoration Stalled in TX
    1984 Capri RS T-top Roller
    1983-84 Gloy Racing Trans Am/IMSA Body Parts

  11. #11
    FEP Senior Member Tigger's Avatar
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    Quote Originally Posted by marcod13 View Post
    Thanks for the reply!
    I will take it apart and post a picture of it on here and maybe you can chime in further to see if there are some bad spots that need to be cleaned? Appreciate you looking for the article!!!

    Thanks!


    Sent from my iPhone using Tapatalk
    Here is the link I was referring too. Originally I took mine apart and just used steel wool to clean the oxidation off the copper terminals. This lasted a short period before it stopped working. I then tinned the leads with solder and have not had any issues with it since. It’s been like 6 years now and my map light still works properly.

    https://www.ascmclarencoupe.com/Proj...htRestoration/
    Last edited by Tigger; 11-13-2019 at 07:05 PM.
    67 Mustang Coupe
    96 Tangerine GT
    86 Saleen #179

  12. #12

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    Quote Originally Posted by wraithracing View Post
    The outside headlights are dual element bulbs. There are three electrical leads on the outer lights. One is ground, one is low beam, and the other is high beam. The inner lights are high beam single element only, therefore they only illuminate when the high beams are on. There are two electrical leads on the inner lights, one for ground and the other for high beam. The Low beam will have the low beam element illuminate on low beam and then switch to the high beam element when you switch for the high beams.

    Sounds to be like the inner lights may be bad, not connected, or something else. I would remove one or both and check to see first if they are connected. Next I would check for power at the pigtail when the high beams are on. If you have power at the pigtail(s), but no actual illumination then most likely the bulbs are bad and should be replaced. If you don't have power at the pigtail, then you will need to check the wiring and figure out why you have no power. The wiring pretty much loops from the low beams to the high beams, so should be an easy check to verify if something is wrong with the wiring. Hope that helps! Good Luck!
    Thanks so much for this direction! This will help me in my quest to sort out this problem.. what is the best approach to get to the hi beams. Need to look closer at the car and get familiar with it. I feel this is a good start, I have a volt meter and I’ll give it a shot this weekend!


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  13. #13

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    Quote Originally Posted by Tigger View Post
    Here is the link I was referring too. Originally I took mine apart and just used steel wool to clean the oxidation off the copper terminals. This lasted a short period before it stopped working. I then tinned the leads with solder and have not had any issues with it since. It’s been like 6 years now and my map light still works properly.

    https://www.ascmclarencoupe.com/Proj...htRestoration/
    Thank you!! This is an awesome resource and glad to hear it worked for you, hope it works for me too!


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  14. #14
    Moderator wraithracing's Avatar
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    Most likely you will need to remove the trim ring retainer for one of the headlights to gain access to the rear plug. There's very little room between the headlight support and the front core support to get the plug loose. There are 4 screws that hold the trim ring in place. Two on the top and two on the bottom. If you want you can remove the top two screws and then carefully pull the trim ring out and down to wiggle the headlight out. Otherwise remove all 4 screws, remove the trim ring, and pull the light out to disconnect the plug on the back. Then test the plug with the high beams on for voltage. If you have power at the plug, then most likely the headlights are bad. Otherwise you have a short or break in the line for the high beam plugs and will need to trace the wire until you find the issue. Good Luck!
    ​Trey

    "I Don't build it hoping for your approval! I built it because it meets mine!"

    "I've spent most of my money on Mustangs, racing, and women... the rest I just wasted."

    Mustangs Past: Too many to remember!
    Current Mustangs:
    1969 Mach 1
    1979 Pace Car now 5.0/5 speed
    1982 GT Stalled RestoModification
    1984 SVO Still Waiting Restoration
    1986 GT Under going Wide Body Conversion Currently

    Current Capris:
    1981 Capri Roller
    1981 Capri Black Magic Roller Basket Case
    1982 Capri RS 5.0/4spd T-top Full Restoration Stalled in TX
    1984 Capri RS T-top Roller
    1983-84 Gloy Racing Trans Am/IMSA Body Parts

  15. #15

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    Quote Originally Posted by wraithracing View Post
    Most likely you will need to remove the trim ring retainer for one of the headlights to gain access to the rear plug. There's very little room between the headlight support and the front core support to get the plug loose. There are 4 screws that hold the trim ring in place. Two on the top and two on the bottom. If you want you can remove the top two screws and then carefully pull the trim ring out and down to wiggle the headlight out. Otherwise remove all 4 screws, remove the trim ring, and pull the light out to disconnect the plug on the back. Then test the plug with the high beams on for voltage. If you have power at the plug, then most likely the headlights are bad. Otherwise you have a short or break in the line for the high beam plugs and will need to trace the wire until you find the issue. Good Luck!
    Thanks so much for the guidance! Will have a look this weekend


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  16. #16

    Default A few light issues on my 1986 GT...

    Okay so with all of the guidance here I’m feeling really confident to find this issue. I went in garage tonight, took out the retainer rings and pulled out the hi beam lamps. Contacts were really corroded I cleaned them up. I then took a 12V trickle charger to test the bulb, One (passenger side) isn’t illuminating. The other one(driver side) does work! So the bulbs seem to function (one at least..), now onto the plugs. They seem really filthy, full of paint overspray, dust, dirt etc. I did put a voltmeter lead into each one and turned on the light switch and then pulled the hi beam switch. Nothing came on nor did the voltage show a spike toward 12v, saw no spike at all actually. The car wasn’t on but I don’t believe it needs to be? The light switch was pulled to the on position and then I pulled the hi beam lever. So what is next? I guess tomorrow I’m testing the light switch? See if all the contacts are 1. Connected and 2. Receiving power.. is there a fuse for the hi beams?

    Thanks in advance everyone!




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  17. #17

    Default A few light issues on my 1986 GT...

    Quote Originally Posted by wraithracing View Post
    Most likely you will need to remove the trim ring retainer for one of the headlights to gain access to the rear plug. There's very little room between the headlight support and the front core support to get the plug loose. There are 4 screws that hold the trim ring in place. Two on the top and two on the bottom. If you want you can remove the top two screws and then carefully pull the trim ring out and down to wiggle the headlight out. Otherwise remove all 4 screws, remove the trim ring, and pull the light out to disconnect the plug on the back. Then test the plug with the high beams on for voltage. If you have power at the plug, then most likely the headlights are bad. Otherwise you have a short or break in the line for the high beam plugs and will need to trace the wire until you find the issue. Good Luck!
    Thanks for your advice. I was able to sort out the driver side headlight tonight. Strange though.. tested the polarity of the connector to the driver side headlight (after I dismantled the connectors and cleaned them) and the polarity was reversed. So I had to plug in the headlight + to the connector - and the headlight - to the connector +. Has anyone had this issue before? Is it okay to leave this way and what would cause it? Gonna try the passenger side tomorrow.. garage is cold!


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    Last edited by marcod13; 01-03-2020 at 10:47 PM.

  18. #18
    FEP Senior Member
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    Polarity does not matter for these types of lights. The power and ground can connect to either side. Only LED's are polarity sensitive.
    Your problem was most likely due to a bad connection.

  19. #19

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    The fog light problem sounds like a bad relay. Its up under the dash and should be silver and have three terminals if I recall right. The 86 wiring diagrams in the EVTM are wrong. The part number should be on it to track down a replacement. But check the rest of the circuit. Work backwards from the bulbs through the wiring to the relay. Use the EVTM just be aware its not totally correct. My 86 GT was also well taken care of but for some reason the fogs didn't work for many years until I began tracing the entire circuit. When they worked it was glorious. Sounds like you are well on your way to solving the problems. Best of luck.

  20. #20

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    Quote Originally Posted by dynodon64 View Post
    Polarity does not matter for these types of lights. The power and ground can connect to either side. Only LED's are polarity sensitive.
    Your problem was most likely due to a bad connection.
    Whew! Glad to know, thanks! The passenger side hi beam connector had corroded contacts so you were correct! Bad news is I need a replacement headlight for the passenger side. Hoping I can get one locally. Thanks for the info!


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  21. #21

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    Quote Originally Posted by Magnetic82 View Post
    The fog light problem sounds like a bad relay. Its up under the dash and should be silver and have three terminals if I recall right. The 86 wiring diagrams in the EVTM are wrong. The part number should be on it to track down a replacement. But check the rest of the circuit. Work backwards from the bulbs through the wiring to the relay. Use the EVTM just be aware its not totally correct. My 86 GT was also well taken care of but for some reason the fogs didn't work for many years until I began tracing the entire circuit. When they worked it was glorious. Sounds like you are well on your way to solving the problems. Best of luck.
    Thank you for the guidance! Yeah I am beginning to lean toward the problem being a bad relay at this point. As I switch on the fog lights I get a sporadic clicking sound but no lighting. Now that I am done with the hi beam headlights I am going to make my way into testing the voltage going to the fogs and will back track the wiring.

    One quick question re: relay.. how do I know if I have a bad relay? Is there any physical way to tell? If I’m not getting voltage to the fogs but hear the sporadic clicking at the switch is that the indication of the relay not sending power to the fogs, thus it is no good? Thanks!


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  22. #22

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    Tested voltage coming off fog light harness it is receiving power. I’m wondering if fog light switch is bad.. haven’t found the relay yet. Will keep at it next weekend.


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  23. #23

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    Switch could be bad. That's not uncommon. The ticking you describe is indicative of a bad relay. Plus if all the other parts of the circuit are good then the relay is usually the culprit. The biggest problem is actually the bulbs- they get cracked and broken easily; also the lenses. Bulbs are cheap. Original lenses are not. Hopefully the wiring between the harness connector under the hood near the front and the switch is good. Then its just a component that's bad.

  24. #24

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    Quote Originally Posted by Magnetic82 View Post
    Switch could be bad. That's not uncommon. The ticking you describe is indicative of a bad relay. Plus if all the other parts of the circuit are good then the relay is usually the culprit. The biggest problem is actually the bulbs- they get cracked and broken easily; also the lenses. Bulbs are cheap. Original lenses are not. Hopefully the wiring between the harness connector under the hood near the front and the switch is good. Then its just a component that's bad.
    Thank you! Happen to give me any direction exactly where the relay is? Great news is that my fog lights work when bench tested! Now I just gotta find some covers for when I install them.


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  25. #25

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    I think the relay is slightly between the steering column and the fog light switch. You'll have to fanagle yourself in there to see upwards- if the seat is out its easier. Relay should be a small silver one cubic inch thing that attaches with a ground screw to a bracket. It should be relatively easy to get at- not like replacing a throttle cable on the top of the pedal. Wires join to the relay with a connector that just pulls off. I don't have any pictures of mine but it wasn't difficult at all. Glad to hear the lights work. Nothing screams eighties like two square headlights and two square fogs below.

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