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Discussion Starter · #1 ·
:eek: I was driving home tonight when my headlights went completely out. The only way I could get them to come on was to pull the high beam switch towards me - while doing this every now and then the low beams would kick in for a couple of seconds and go back out. When I got home, the lights would come on for a few seconds here and there.

All other lights work as normal. I checked all fuses related to the headlights inside both the car and the engine compartment - all were fine. The only warning I got was every once and awhile, I would notice that the left light would seem to flicker every once and awhile while driving. In searching the threads I found some past issues with headlights and the "multifunction switch". Any help you can offer would be greatly appreciated.

Sincerely,

Fred

TB 3405
24,000 miles
 

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since you checked the fuses everywhere, my guess would be the multi function switch since both lights are being affected and when you fiddle with the multi switch, you get some response. you might drive by a Ford dealer and ask to talk to their electrical guy. usually every dealer has a guy who specializes in electrical gremlins.....tell him and see what he says.
 

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Discussion Starter · #4 ·
Thanks for the assistance. After doing more research the most likely culprit is the multifunction switch. I called my closest Ford dealer today and they said the phrase everyone dreads, "I'm not quite sure, but leave it for the day and we will try and find the problem".

Again, if anyone has had the same exact symptoms - please let me know what was needed to fix it.
 

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You're money ahead to _guess_ at a couple parts to replace yourself, than leaving it at a dealer for $50+ an hour to "troubleshoot" for you. This is even a risky proposition (electrical diagnosis) when your car is at a garage *you trust*, because noone knows how long it may take to figure it out.
 

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Didn't you say that one light was flickering and the other wasn't at times? That sounds more like a loose connections/short rather than a switch. The switch is going to either send power to both lights or none at all, not just one or the other.
 

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I would put money on the multi function switch. The high and low beams are controled by it, as are the directionals. I'm not clear as to which "left" light flickers, though. Is it the headlight or the turn signal?

Either way, the switch is kinda easy to replace. Hardest part would be getting the shroud off of the steering column. Couple of screws from the bottom, and it unsnaps. Then a few more screws and the switch comes off, and unplugs. The installation is the reverse of the procedure.
 

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Discussion Starter · #8 ·
I bought a new multifunction switch today, installed it, and after 2 minutes of both headlghts being on I had the same problem - they both went out (all other lights still remained on). I then put the original switch back in and started really focusing on the headlight bulbs. Upon examination, both looked fine. However, if I took the left one out, the right one would stay on full time. I then took the good right bulb and put it in the left socket - it stayed on!

To double check what I thought was going on (bad left bulb - even though it looked fine), I then put the "suspect" original left bulb in the right socket and both lights stayed on for about 2 minutes and then both kicked off again. Problem solved, right - WRONG!

I bought two brand new bulbs put everything back in place, and the lights stayed on for about 10 minutes BEFORE BOTH KICKED OFF AGAIN - IT DOESN'T SEEM TO MAKE SENSE!

Any advice now?
 

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Is the car running or turned off?
If you look at the post that has the schematic drawing there are two fuses in the central junction box under the dash number 10 and number 4 which are both ten amp. At this point there are seperate circuits for each lamp so it would most likely be before that. I would put a test lamp on both side of both fuses and see if the test lamp flicker at the same time as the lights, if it does then we have to back up farther towards the battery.

The commonality between the two lamps before the fuses is the mutltifunction switch which you replaced. Then the Headlight switch then you go back to top of the page and it reads HOT AT ALL Times connection. This will come from the power junction fuse box next to the battery. If Mid Life Crisis #388 could post up the wiring diagram for central fuse box and alternator is would help me narrow this down.

In the old days the fuseable link was typically on the HOT side of the starter solenoid. Usually a BIG red or black wire and about two inched down the wire get a bit smaller with what appears to be black heat shrink, that is the link. Now on our car there is a big black wire with an orange strip that goes to the input of the central fuse box. This black wire with orange strip goes into a small white piece that has Fuseable link printed right on it then this turns into two beige wires that go into the power distribution fuse box next to the battery.

This sounds like there is severe corrison on a fuse, a burnt wire, a burnt fuseable link or a fuse that has the internal element that is broken. (When it is cold it relaxs and touches when it gets warm it moves and opens the circuit, same way the old turn signal flasher work.) After looking at my car, the fusable link is between the alternator and the central fuse box so it isn't likely this is the cause if the car is not running. This is because if the car is off the big red wire coming from the battery to the central fuse box is providing power. My owners manual on page 136shows that the fuse 2 30 Amp MAXI fuse (green) closest to the engine center row is the fuse for the low beam head lamps circuit. The drawing shown in the manual shows the latch and hinge for the central fuse box backwards. So i pulled fuse 2 closest to the engine in the middle row and my headlight quit working.

Pull this fuse out and look down at the mating connections. Look for corrision overheating or a defective fuse, or swap it with fuse ten which is for the parking lamp.

You can also put a test lamp on fuse two on the power distribution box next to the battery, one side at a time and see if it flickers on either side when the headlights flicker. This fuse is hot all the time but no current going thru until you turn on the headlight.

The last thing would be to disconnect the battery and turn the power distrubtion box over and look at the connections on the bottom for burnt or loose wires.

Sorry so long winded, but that is why electronic guys get so much per hour. :) 30+years working on DOD long range mobile radars.
 

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I can't find the thread but years ago someone had a crazy electrical problem and a ford service member said that there were lots of problems with the connections at the back of the fuse block. Sure enough that was where the problem was. He gave instructions on the best way to make the repair if I remember.

Not related but just FYI there were serveral Bullitts that also lost all power and that was tracked down to a junction under neath the batter or right in that area that was loose.
 

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Well, since the multi function switch didn't fix the problem:redface: , and the fuses look good, and new bulbs did't fix the problem:doubt: , hmm.......

Here goes a theory.:idea: If you remove only ONE bulb, and the problem goes away, then I am going to say the headlight switch is bad. Here's my thoughts on why-

When new, the bulbs in our headlights draw around 5 amps a peice, for a total of 10 amps (that's why they are fused at that rating and why most good HID kits have a separate fused line that goes to the battery as they pull around 20 amps.) The headlight switch is probably rated, when new, at around 12 or 13 amps (most engeneers allow some "extra" in electrical design.) If the headlight switch is going bad, just not completely, it may be able to pass 6 or 7 amps with no problem but not 10. While trying to pass 10 amps, it will work for a moment but quickly shut off as the cicuit just fails. It also makes sense that with only one bulb in, it would work for quite a while. This would also explain the "flash to pass" circuit working, as it pulls power from a totally different fuse, and does not go through the headlight switch at all.

So might I suggest inspecting the light switch. Coud be one of two problems with it- the actuall switch (which is very easy to change) and the harness (not so much). I have only seen on harness problem in my years so I put it out for a possibility. If the harness looks fine, and does not look "burned" at all, then I would look at the switch itself.

Keep us posted!
 

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Rule of thumb is a fuse or circuit breaker should only be at 75-80 percent load rating. I agree it could be the headlight switch, again look for discolored wires or melted plastic. The test light having steadly light on the power distribuiton box by battery and the headlight flikering would leak down the line toward the headlight switch.

Also agree with IM. If only one headlight is plugged in the current draw will be less and bad/burnt/corroded connection will let the smaller current draw pass then as the current draw gets higher the flickerig will start.

Try swapping the fuses to narrow down that part of the circuitry. I have had three bad/intermittant fuses in 30years of troubleshooting. You don't forget those kind of problems.
 

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Discussion Starter · #15 ·
All is of the well-thought through responses/pictures/schematics are one of the many things I like about this community. I removed the light switch and found a melted spot in the harness. However, there is a broken piece jingling around the inside of the switch itself. Since it is a completely sealed unit, I cannot see what is rattling around unless I break it.

Again, since the problem really come on so suddenly, it is a low mileage always garaged car, and all other connections/fuses appear to be fine - should a new light switch do the trick?

The reason I ask is that the Ford dealership says no return on electrical parts (I will have to use all of my charm to get them to take the multifunction switch back).

MAANY THANKS!!!!
 

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Voldadof2 said:
All is of the well-thought through responses/pictures/schematics are one of the many things I like about this community. I removed the light switch and found a melted spot in the harness. However, there is a broken piece jingling around the inside of the switch itself. Since it is a completely sealed unit, I cannot see what is rattling around unless I break it.

Again, since the problem really come on so suddenly, it is a low mileage always garaged car, and all other connections/fuses appear to be fine - should a new light switch do the trick?

The reason I ask is that the Ford dealership says no return on electrical parts (I will have to use all of my charm to get them to take the multifunction switch back).

MAANY THANKS!!!!
not sure.....junkyard for a switch
 

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Discussion Starter · #17 ·
Good and bad news.....

I had a friend come over and weput his switch in mine and it worked! Then I put my switch in his and it worked! I then went back to my car and the ceramic piece on the unit that is about the size of a half-dollar was smoking hot while the other one in his car remained cool. I checked every other connection I could find and didn't find any issues - something is not right somewhere.....

I guess it is off to the dealer - joy of joys!!!
 

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I will have to look at my wiring scematics after I get to work in the morning to know, but what color was the wire that was discolored? If that circuit was "grounding out" it would cause a spike in current (amps) without causing a blown fuse like a complete short would. Let me know what color that wire is and I will get back to you.
 

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Sorry for the delay. Looks like the most up to date info I have on Mustangs is up to '98, and it looks like things were changed in '99 with the change in body style, as well as electrical systems. The only blue/orange listed in that diagram for lighting is the hot all the time for the flash to pass system, so I think that maybe it is all wrong. I'll talk to my buddy at the Ford dealer in the morning and get a more up to date print out, and maybe som insight.
 
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