light failure

slowpoke

slowpoke

Registered User
i assume like everything else on this car the headlights run off of a relay, anyone know where the relays for the headlights are located?
 
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I dont know about a relay but its always the MFS or the head light switch that causes them to go on and off with no warning. Try wiggeling the MFS next time they go out and see if they come back on. If so replace switch.
 
.......this is the 'Power Control Box' (under the hood, next to the battery) layout for a 1990 SC.

Been running your fog lights all the time...?
 

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slowpoke said:
i assume like everything else on this car the headlights run off of a relay, anyone know where the relays for the headlights are located?
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LH side of the console behind the lower panel(s) on the driver's side. There are 2 relays. Its the one that will click when you move the headlight switch on/off. Much easier to work on if you remove the panels. Be careful with the plastic outer panel as the clips tend to get hung up in the rusty hole they clip into and snap off of the panel. :( Keep some epoxy handy.
 
What are your symptoms? Do the lights just straight up not work or do they flash? My headlights flashed for a while until I changed the headlight switch, now they work fine. Could also be MFS or a relay like others said.
 
There is no relay in the headlight system which is why the multi function switch, which carries all the load, has a short lifespan.

More than likely it's the multifunction switch... Do the lights work if you try the "flash to pass" or hi beams?
 
bigpoppa822 said:
What are your symptoms? Do the lights just straight up not work or do they flash? My headlights flashed for a while until I changed the headlight switch, now they work fine. Could also be MFS or a relay like others said.
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they flash on and off, or they did last night. if i wiggle they switch no help, if i shut it all the way off and back on they work. im thinking the relay might have fluid and due to freezing weather hear now the relay might be froze. might not help they i just found the batt ground wire was lose to. its tight now, and i got a 5gal bucket of relays. ill swap it and see what happens.
 
TbirdSCFan said:
LH side of the console behind the lower panel(s) on the driver's side. There are 2 relays. Its the one that will click when you move the headlight switch on/off. Much easier to work on if you remove the panels. Be careful with the plastic outer panel as the clips tend to get hung up in the rusty hole they clip into and snap off of the panel. :( Keep some epoxy handy.
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TY for the loc on the relays:)
 
KMT said:
.......this is the 'Power Control Box' (under the hood, next to the battery) layout for a 1990 SC.

Been running your fog lights all the time...?
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the fog lights are after market now and i ran a new relay system for them, so they are not on the head light system now. i can run them without the lights on thankfully due to what happened last night lol.
 
SCTBIRD1173 said:
There is no relay in the headlight system which is why the multi function switch, which carries all the load, has a short lifespan.
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Actually, the headlight relay is clipped to the console frame. The MFS doesn't carry the full current for either low or high beams. It wears, but not from high current. For example, my DD has almost 250000 with the original MFS.
 
TbirdSCfan,

I was always told there wasn't a relay in earlier Fords... If there was a relay in say... my 95 Taurus, why is the hardshell on the headlight switch melted? I don't even use the headlight switch! It has auto lamps! :D

Anyway, thanks for the information, I'm going to look in my EVTM for this elusive headlight relay tonight... :cool:
 
SCTBIRD1173 said:
TbirdSCfan,

I was always told there wasn't a relay in earlier Fords... If there was a relay in say... my 95 Taurus, why is the hardshell on the headlight switch melted? I don't even use the headlight switch! It has auto lamps! :D

Anyway, thanks for the information, I'm going to look in my EVTM for this elusive headlight relay tonight... :cool:
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having a relay doesnt mean you cant have a short or faulty switch that can melt, all a relay really does is makes it easier to control high amp components without having to run alot of big wire. the average relay switch can power 30amps and only needs about .015amp to activate it. relays are great to use but also need some loven from time to time to.
 
SCTBIRD1173 said:
TbirdSCfan,

I was always told there wasn't a relay in earlier Fords... If there was a relay in say... my 95 Taurus, why is the hardshell on the headlight switch melted? I don't even use the headlight switch! It has auto lamps! :D

Anyway, thanks for the information, I'm going to look in my EVTM for this elusive headlight relay tonight... :cool:
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You bring up an interesting point. Well, I would have to say that the cars with the auto lamp module use a relay for both low + high beams. That relay may tie back into the headlight switch itself. I will have to look at my black car which doesn't have the auto lamp/dimmer to see how its set up. I suppose its possible that they didn't use one in that setup.
 
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Ok guys, I checked the EVTM for my 1990 SC...

Cars w/out autolamp DO NOT have a relay at all. All the load from the headlights go directly through the headlamp switch and the MFS. We are talking a 60amp and a 20amp "hot at all times" circuit feeding directly through both switches. Bad design on Ford's part there.

As far as cars with autolamp, it's not that much different... There is still full headlight load being carried through the MFS. As well as it still has a DIRECT connection to both the 60amp and 20amp "hot at all times" circuits. It appears that the relay within the autolamp circuit is there just to protect some of the autolamp components (as far a I can tell atleast). It doesn't sit between the MFS and direct headlamp draw which makes me again wonder what Ford was thinking here.

I've owned a lot of Fords between my wife and I, not everyone of them had a bad multifunction switch but any one of them that ever had a headlight issue it was the MFS. Thats just my past experience and my .02 cents on this subject... :D
 
KMT said:
>i ran a new relay system for them

Any other mods to the electrical and/or lights?
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lots of mod to the elect, mostly for the sound system. as for the lights! no thats the only mod to the lights so far. if indeed the last post is correct then ill run a new relay system for the lights aswell.
 
>lots of mod to the elect, mostly for the sound system

I was running my stereo @ max. volume (engine off) testing some new 3-ways the other day - lowered both windows at the same time and when they hit bottom the head unit clipped. First time ever. It reset and came right back, but I think I pushed a lower threshold on the electrical supply.

Keep us posted and good luck.
 
TbirdSCFan said:
You bring up an interesting point. Well, I would have to say that the cars with the auto lamp module use a relay for both low + high beams. That relay may tie back into the headlight switch itself. I will have to look at my black car which doesn't have the auto lamp/dimmer to see how its set up. I suppose its possible that they didn't use one in that setup.
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I stand corrected. The relay is part of the autolamp circuit. My 90 5speed doesn't have one. therefore the current is switched through the dash switch. Also means that the MFS is passing some current as well. My MFS is probably OK due simply to not using it all that much. :)
 
not to hijack but has anyone cross refrenced our headlight switches with other ford models? wondering if there is a better option for this so it doesn't end up burning one of our sc's to the ground.
 
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